I tried to activate my office with a persnoak working kms of mine.

c:\Program Files\Microsoft Office\Office16>cscript ospp.vbs /act
Microsoft (R) Windows Script Host Version 5.812
Copyright (C) Microsoft Corporation. All rights reserved.

---Processing--------------------------
---------------------------------------
Installed product key detected - attempting to activate the following product:
SKU ID: 85dd8b5f-eaa4-4af3-a628-cce9e77c9a03
LICENSE NAME: Office 19, Office19ProPlus2019VL_KMS_Client_AE edition
LICENSE DESCRIPTION: Office 19, VOLUME_KMSCLIENT channel
Last 5 characters of installed product key: 6MWKP
ERROR CODE: 0x80070005
ERROR DESCRIPTION: Run the following: cscript ospp.vbs /ddescr:0x80070005
NOTICE: A KB article has been detected for activation failure: 0x80070005
FOR MORE INFORMATION PLEASE VISIT: https://support.microsoft.com/kb/2870357#Error0x80070005
---------------------------------------
---------------------------------------
---Exiting-----------------------------

I checked in the web and I tried to change the key's permission in safe mode:

Computer\HKEY_USERS\S-1-5-20

I tried to enable network service full control and checked the option to change all the subkeys. and I get the error that registry editor cannot set security in the key selected , or some of its subkeys.

does anyone have a clue how to solve this issue? the office activation fails.

The solution might be in the Microsoft article Resolve Windows activation error codes:

0x80070005 Access denied

The full text of this error message resembles the following:

Access denied. The requested action requires elevated privileges.

Possible cause

User Account Control (UAC) prohibits activation processes from running in a non-elevated Command Prompt window.

Resolution

Run slmgr.vbs from an elevated command prompt. To do this, on the Start menu, right-click cmd.exe, and then select Run as administrator.

In your case, run the Office activation as Administrator, and it might work this time.