sybase interactive sql initialization error (java path)

Getting this error, from the looks of which it's a missing classpath. Trying to force the classpath via setting it like below doesn't help.

set CLASSPATH=C:\Sybase\Shared\SAPJRE-8_1_008_64BIT\lib

This is a relatively fresh installation of Sybase IQ, and I'm trying to run the Interactive SQL from the program list.

C:\Sybase\IQ-16_1\Bin64>dbisql.com
Error occurred during initialization of VM
java/lang/NoClassDefFoundError: java/lang/Object
[Last 4000 events in the event buffer]
  <thread>                      <time>  <id>          <description>
 23548                            0.00  0x00000001    Creating red and yellow zone [0x0000008890e00000,0x0000008890e04000]
Aborting  ...

Curious if there's a way to debug it through an elevated verbose level - to see which class is not being found. Very odd that a new installation would do that. Windows 10 environment, compatible with IQ 16.x