How to erase and flash STM32L4xx

i have a problem with a STM32L431KB, but i am new in reference to STM.

The uC is new and is basically recognized by the ST-Link utility / STM32CubeProgrammer detected (Device, Type, ID, Flash Size, CPU, Target Vdd...).

However, it cannot be programmed. After some attempts with the ST-Link Utility I switched to the STM32CubeProgrammer with the same issue.

The following error: The uC can't be deleted (neither the total nor individual sectors). Also the option Bytes can't be manipulated too.

Attempting to flash the .elf file, the following is logged by CubeProgrammer:

15:18:57:180 : Memory Programming ...
15:18:57:181 : Opening and parsing file: Test.elf
15:18:57:182 : File : Test.elf
15:18:57:182 : Size : 864 Bytes
15:18:57:183 : Address : 0x08000000
15:18:57:183 : Erasing Segment <0> Address <0x08000000> Size <864>Bytes
15:18:57:183 : Erasing memory corresponding to segment 0:
15:18:57:183 : Memory erase...
15:18:57:186 : reset ap 0
15:18:57:186 : halt ap 0
15:18:57:186 : w ap 0 reg 15 (0x20000000)
15:18:57:188 : w ap 0 reg 17 (0x20000500)
15:18:57:188 : w ap 0 reg 16 (0x01000000)
15:18:57:195 : w ap 0 @0x20000D00 0x00000200 bytes
15:18:57:195 : w ap 0 @0x20000000 0x00000004 bytes
15:18:57:220 : w ap 0 @0x20000004 0x000008C8 bytes
15:18:57:221 : Erasing internal memory sector 0
15:18:57:221 : Init flashloader...
15:18:57:221 : halt ap 0
15:18:57:221 : w ap 0 reg 0 0x00000001
15:18:57:222 : w ap 0 reg 1 0x00000000
15:18:57:222 : w ap 0 reg 2 0x00000000
15:18:57:222 : w ap 0 reg 3 0x00000000
15:18:57:222 : w ap 0 reg 4 0x00000000
15:18:57:222 : w ap 0 reg 5 0x00000000
15:18:57:222 : w ap 0 reg 6 0x00000000
15:18:57:222 : w ap 0 reg 7 0x00000000
15:18:57:222 : w ap 0 reg 8 0x00000000
15:18:57:227 : w ap 0 reg 9 0x00000000
15:18:57:234 : w ap 0 reg 10 0x00000000
15:18:57:237 : w ap 0 reg 11 0x00000000
15:18:57:237 : w ap 0 reg 12 0x00000000
15:18:57:239 : w ap 0 reg 13 0x00000000
15:18:57:239 : w ap 0 reg 14 0x20000001
15:18:57:239 : w ap 0 reg 15 0x20000005
15:18:57:239 : w ap 0 reg 16 0x01000000
15:18:57:241 : w ap 0 reg 17 0x20000CC8
15:18:57:241 : w ap 0 reg 18 0x00000000
15:18:57:241 : run ap 0
15:19:02:004 : halt ap 0
15:19:02:004 : Init function fail with timeout
15:19:02:004 : r ap 0 reg 16 0x81000000
15:19:02:004 : Loader sector erase...
15:19:02:004 : Error: failed to erase memory
15:19:02:037 : Error: failed to erase memory

If I activate the option "Skip flash erase before programming", i receive the following:

15:19:19:733 : Memory Programming ...
15:19:19:733 : Opening and parsing file: Test.elf
15:19:19:734 : File : Test.elf
15:19:19:735 : Size : 864 Bytes
15:19:19:735 : Address : 0x08000000
15:19:19:735 : Download in Progress:
15:19:19:735 : Size : 864 Bytes
15:19:19:735 : Address : 0x08000000
15:19:19:736 : Buffer program...
15:19:19:741 : reset ap 0
15:19:19:741 : halt ap 0
15:19:19:741 : w ap 0 reg 15 (0x20000000)
15:19:19:742 : w ap 0 reg 17 (0x20000500)
15:19:19:742 : w ap 0 reg 16 (0x01000000)
15:19:19:747 : w ap 0 @0x20000D00 0x00000200 bytes
15:19:19:747 : w ap 0 @0x20000000 0x00000004 bytes
15:19:19:764 : w ap 0 @0x20000004 0x000008C8 bytes
15:19:19:765 : Loader write range...
15:19:19:771 : w ap 0 @0x20000D00 0x000001B0 bytes
15:19:19:771 : W B1 in RAM @0x20000D00 size 0x000001B0 : 0004ms
15:19:19:771 : Init flashloader...
15:19:19:771 : halt ap 0
15:19:19:772 : w ap 0 reg 0 0x00000001
15:19:19:772 : w ap 0 reg 1 0x00000000
15:19:19:774 : w ap 0 reg 2 0x00000000
15:19:19:779 : w ap 0 reg 3 0x00000000
15:19:19:779 : w ap 0 reg 4 0x00000000
15:19:19:779 : w ap 0 reg 5 0x00000000
15:19:19:779 : w ap 0 reg 6 0x00000000
15:19:19:780 : w ap 0 reg 7 0x00000000
15:19:19:780 : w ap 0 reg 8 0x00000000
15:19:19:780 : w ap 0 reg 9 0x00000000
15:19:19:780 : w ap 0 reg 10 0x00000000
15:19:19:780 : w ap 0 reg 11 0x00000000
15:19:19:781 : w ap 0 reg 12 0x00000000
15:19:19:781 : w ap 0 reg 13 0x00000000
15:19:19:786 : w ap 0 reg 14 0x20000001
15:19:19:786 : w ap 0 reg 15 0x20000005
15:19:19:790 : w ap 0 reg 16 0x01000000
15:19:19:797 : w ap 0 reg 17 0x20000CC8
15:19:19:797 : w ap 0 reg 18 0x00000000
15:19:19:797 : run ap 0
15:19:24:000 : halt ap 0
15:19:24:000 : Init function fail with timeout
15:19:24:004 : r ap 0 reg 16 0x41000000
15:19:24:004 : w ap 0 @0x20000EB0 0x000001B0 bytes
15:19:24:004 : W B2 in RAM @0x20006500 size 0x000001B0: 4236ms
15:19:24:010 : r ap 0 reg 0 0x48000000
15:19:24:012 : reset ap 0
15:19:24:012 : halt ap 0
15:19:24:012 : w ap 0 reg 15 (0x20000000)
15:19:24:014 : w ap 0 reg 17 (0x20000500)
15:19:24:014 : w ap 0 reg 16 (0x01000000)
15:19:24:020 : Loader write range...
15:19:24:026 : w ap 0 @0x20000D00 0x000001B0 bytes
15:19:24:026 : W B1 in RAM @0x20000D00 size 0x000001B0 : 0004ms
15:19:24:027 : halt ap 0
15:19:24:027 : r ap 0 reg 0 0x00000000
15:19:24:027 : Error: failed to download Segment[0]
15:19:24:027 : Error: failed to download the File
15:19:24:048 : Time elapsed during download operation: 00:00:04.284
15:19:24:048 : Verifying ...
15:19:24:048 : Read progress:
15:19:24:049 : Reading data...
15:19:24:053 : r ap 0 @0x08000000 0x00000360 bytes
15:19:24:054 : Error: Data mismatch found at address 0x08000000 (byte = 0xFF)
15:19:24:054 : Error: Download verification failed

Also the "Option Bytes" can't be changed, i tested it with BOR-Level:

15:21:44:241 : Option byte command : -ob BOR_LEV=4
15:21:44:244 : PROGRAMMING OPTION BYTES AREA ...
15:21:44:244 : r ap 0 @0x40022040 0x00000004 bytes
15:21:44:244 : Bank : 0x00
15:21:44:244 : Address : 0x40022020
15:21:44:244 : Size : 20 Bytes
15:21:44:296 : Buffer program...
15:21:44:301 : reset ap 0
15:21:44:301 : halt ap 0
15:21:44:301 : w ap 0 reg 15 (0x20000000)
15:21:44:302 : w ap 0 reg 17 (0x20000500)
15:21:44:302 : w ap 0 reg 16 (0x01000000)
15:21:44:308 : w ap 0 @0x20000D00 0x00000200 bytes
15:21:44:309 : w ap 0 @0x20000000 0x00000004 bytes
15:21:44:327 : w ap 0 @0x20000004 0x000008C8 bytes
15:21:44:329 : w ap 0 @0x20000D00 0x00000014 bytes
15:21:44:330 : Loader write option bytes...
15:21:44:330 : Init flashloader...
15:21:44:330 : halt ap 0
15:21:44:334 : w ap 0 reg 0 0x00000001
15:21:44:334 : w ap 0 reg 1 0x00000000
15:21:44:334 : w ap 0 reg 2 0x00000000
15:21:44:335 : w ap 0 reg 3 0x00000000
15:21:44:335 : w ap 0 reg 4 0x00000000
15:21:44:335 : w ap 0 reg 5 0x00000000
15:21:44:337 : w ap 0 reg 6 0x00000000
15:21:44:342 : w ap 0 reg 7 0x00000000
15:21:44:342 : w ap 0 reg 8 0x00000000
15:21:44:342 : w ap 0 reg 9 0x00000000
15:21:44:342 : w ap 0 reg 10 0x00000000
15:21:44:342 : w ap 0 reg 11 0x00000000
15:21:44:344 : w ap 0 reg 12 0x00000000
15:21:44:344 : w ap 0 reg 13 0x00000000
15:21:44:344 : w ap 0 reg 14 0x20000001
15:21:44:344 : w ap 0 reg 15 0x20000005
15:21:44:344 : w ap 0 reg 16 0x01000000
15:21:44:344 : w ap 0 reg 17 0x20000CC8
15:21:44:344 : w ap 0 reg 18 0x00000000
15:21:44:345 : run ap 0
15:21:49:000 : halt ap 0
15:21:49:000 : Init function fail with timeout
15:21:49:003 : r ap 0 reg 16 0x81005800
15:21:49:003 : WriteOB function terminated with connection error due to OB_Launch
15:21:49:003 : Reconnecting...
15:21:50:103 : STLinkUSBDriver.dll loaded
15:21:50:103 : ST-LINK SN : 066BFF504955857567125335
15:21:50:104 : ST-LINK FW : V2J33M25
15:21:50:111 : Voltage : 3.05V
15:21:50:115 : SWD freq : 4000 KHz
15:21:50:115 : Connect mode: Normal
15:21:50:115 : Reset mode : Hardware reset
15:21:50:167 : Device ID : 0x435
15:21:50:168 : Reconnected !
15:21:50:168 : Success with Time elapsed during Reconnect: 66 ms
15:21:50:223 : UPLOADING OPTION BYTES DATA ...
15:21:50:223 : Bank : 0x00
15:21:50:224 : Address : 0x40022020
15:21:50:225 : Size : 20 Bytes
15:21:50:225 : Reading data...
15:21:50:228 : r ap 0 @0x40022020 0x00000014 bytes
15:21:50:228 : OPTION BYTE PROGRAMMING VERIFICATION:
15:21:50:228 : Error: Expected value for Option Byte "BOR_LEV": 0x4, found: 0x0
15:21:50:254 : Error: Option Byte Programming failed
15:21:50:328 : Option byte refresh
15:21:50:399 : UPLOADING OPTION BYTES DATA ...
15:21:50:400 : Bank : 0x00
15:21:50:400 : Address : 0x40022020
15:21:50:400 : Size : 20 Bytes
15:21:50:400 : Reading data...
15:21:50:400 : r ap 0 @0x40022020 0x00000014 bytes

The Byte options are read out as described in the image. Here I changed nothing (except for the failed BOR test), but I don't know whether the settings are right.

As hardware i use the ST-Link/V2-1 of a Nucleo board (firmware has been updated). The STM itself is only wired with the Vdd/Vref as well as 4 lines to the SWD port (SWDIO, SWCLK, nRST, GND)

Does anyone have any idea what I'm doing wrong...

option bytes