Phenomenon

We confirmed that “Allow display over other apps” is disabled for devices with Android 15.

Cause

There was a change that “Display over other apps” is categorised for restricted apps from Android 15.

We are currently working on fixing this issue.

As a temporary workaround until the fixes are complete, it is possible to resolve this issue by the following steps.

Select the installed apps on the “Display over other apps” page and press the “OK” button on the dialog that says “App was denied access”.
Open “Settings” > “Apps” on your device and select the installed app.
Tap “Allow restricted settings” from the Kebab Menu on the right top.

By following the steps above, ”Allow display over other apps” will become enabled.

Please review the following Google official documentation for more information.