Facebook OAuth Login Error: "This app needs at least one supported permission"

Question

Title:

Facebook OAuth Login Error: "This app needs at least one supported permission" in Test Mode

Content:

I am working on a Facebook Business App that is currently in Test Mode. The Facebook Login integration was working fine a week ago, but now I am getting the following error when trying to log in:

It looks like this app isn’t available. This app needs at least one supported permission.

Things I have checked so far:

1. App Status & Permissions
   • My app is still in Test Mode.
   • I checked App Review > Permissions and Features, and the required permissions are listed but not approved yet.
2. OAuth Settings
   • "Client OAuth Login" and "Web OAuth Login" are enabled in Facebook Login > Settings.
   • The Valid OAuth Redirect URIs field is correctly set.
3. API Version & Deprecations
   • The error page URL shows v13.0. Could this be an issue? Should I update the API version?
4. Business Verification
   • My app is linked to a Business Manager account, but it is still in test mode. Does business verification affect test mode apps?
5. Switching to Live Mode
   • I haven't switched to Live Mode yet since I want to test the app before submitting it for review.

Questions:

• Why did my Facebook Login stop working in Test Mode?
• Does Facebook remove permissions for test apps over time?
• Should I update the API version in my app settings?
• Is business verification required even for Test Mode apps?

Any help would be greatly appreciated! Thanks in advance.