After a Windows 11 update, the client side debugging browser page has gone completely blank for me with no logging/event viewer information. Was working fine previously, I have made no changes to manifest or .debug file since it was working.
Illustrator Version: 29.5.1
CSXS Version: 12.0
Windows 11 Build: 24H2 26100.3775
It may be caused by Illustrator 29.5 (CEP 12). Have you set the PlayerDebugMode for CEP 12?
defaults write com.adobe.CSXS.12 PlayerDebugMode 1
Reference: CEP Panels won’t load in Illustrator 29.5
Yes, that value in my Windows registry is set to 1. The client debugger was working just fine before my Windows 11 update and I have made no changes since.
I see, then there is no more information I can provide.
Since this is the UXP forum for InDesign, you might get more responses if you post in the Illustrator or Exchange categories of the Adobe Community.
The Illustrator team also reads bugs in their prerelease forum: Adobe Prerelease
You might try a couple different versions of Illustrator for comparison.
@ScottyAdobe I think this is already being tracked as AI-4318037
Thank you for linking to that issue! We were running into that exact problem and thought we were doing something wrong. 
Hello again!
The Illustrator team says this is now fixed, even in the beta.