If you try to begin a Focus Lock session and the app isn't working as expected, follow these steps:
Go to your iPhone's Settings
Search for the the Focus Lock app
Enable the Screen Time Restrictions (on)
Note: If you don't see the Screen Time Restrictions option you may have to uninstall and reinstall the app.
If you're still having trouble (eg. only some apps are being blocked, or none at all) then follow these steps to resolve:
Re-enable screen time settings on your iPhone: Head to your iPhone settings, select screentime, scroll down and tap "turn off screentime", then turn it on again and set up your screen time preference.
Double-check your always-allowed apps on the screen time settings to ensure the apps you want to block are not listed there.
Make sure Focus Lock has access to Screentime - Go to your iPhone settings, find Focus Lock and make sure the app has Screentime restrictions enabled.