CWA for Windows 2603 ARM64 is successfully installed in a ARM64-based Windows 11 client machine.
When launching a resource without App Protection enabled for the corresponding delivery group, everything works as expected.
However, when launching a resource with App Protection enabled, an application error dialog is prompted, pointing to Citrix.DesktopViewer.App.exe with error message "An attempt was made to execute an illegal instruction (0xc000001d) occurred in the application". Once clicking “OK” on the application error dialog, another one will be prompted, pointing to a different application. This is an endless loop and most of the applications running in the client machine (whatever belonging to Citrix, Microsoft or other vendors) start to suffer the illegal instruction exception.

Once the issue is triggered, the client machine may turn to completely unusable, i.e., common administrative tools like Command Prompt, Control Panel and Task Manager cannot be opened, and rebooting OS cannot make a recovery either.

Avecto Privilege Guard (now known as "BeyondTrust Endpoint Privilege Management") is running on the ARM64-based Windows 11 client machine.
The illegal instruction exception affecting most applications is a consequence of driver conflict (API hooking) between Citrix App Protection and Avecto Privilege Guard.

The issue is addressed by taking the following steps in the impacted ARM64-based Windows 11 client machine.
1. Remove both Avecto Privilege Guard and CWA for Windows 2603 ARM64
2. Re-install CWA for Windows 2603 ARM64
3. Then, the resource with App Protection enabled can be successfully launched by CWA and the illegal instruction exception no longer occurs on any applications.

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