Thank you for bringing this issue to our attention, and I apologize for the inconvenience you've faced with Illustrator Beta v28.0.
To resolve this, I recommend the following steps:
Uninstall the current Illustrator Beta version.
Restart your device to ensure a clean slate.
Open the Creative Cloud app on your computer.
In the Creative Cloud app, navigate to the Beta Apps section.
Here, you should find the latest beta version released today, which is available for download, i.e., v28.0.42. This version addresses various issues and improvements.
These steps should help you get the latest working version of Illustrator Beta. Please don't hesitate to reach out if you encounter any further issues during this process or have additional questions. We're here to assist you.