Review Downtime separately
Downtime can make an app unavailable during its scheduled hours even if an App Limit still has time left. Conversely, an App Limit does not automatically create a Downtime schedule. Check both rather than assuming one setting controls the other.
Check the exact app or category
For a reliable test, set a short limit on one specific app. A category selection can include more or fewer apps than you expect, while a group of selected apps shares time. If one app is the problem, an individual App Limit makes the result clearer.
Review Share Across Devices
With Share Across Devices enabled, Screen Time limits, schedules, and usage data are shared across devices signed in to the same Apple Account. If a limit is reached unexpectedly, check whether another device is contributing usage. Turn the setting off if each device needs separate Screen Time settings.
Test before rebuilding
Create a short temporary App Limit for a single nonessential app and test it. If the test behaves correctly, recreate only the original rule. If Screen Time still behaves unexpectedly after the settings are correct, update iOS, restart the iPhone, and consider Apple Support for device-specific help.