Check whether the limit is actually still there
Settings, Screen Time, App Limits. A limit that has been deleted looks exactly like a limit that stopped working, and deleting one is two taps you might not remember making.
If the limit is gone and you did not remove it, somebody with the passcode did, or Screen Time was switched off and back on, which clears them.
Check that the time zone and the day boundary agree
Limits reset at midnight in the phone's time zone. Travel, or a phone set to the wrong region, moves that boundary and makes a limit look like it lifted early.
The same goes for a limit set to Every Day versus specific days. A weekday limit does nothing on Saturday, which is exactly when you will notice it missing.
Check Downtime against App Limits
They are separate systems and they interact confusingly. Downtime blocks everything except what you allow. App Limits block specific things after a quota.
An app in Always Allowed is exempt from Downtime no matter what, and people put things there months ago and forget. That list is the first place to look when one specific app is never blocked.
- Always Allowed overrides Downtime entirely.
- A limit and Downtime can both be on, and the more permissive one wins for that app.
- Communication limits are a third system again, and only cover calls and messages.
Check whether the passcode is being asked for at all
If the block appears and lets you through without a passcode, Screen Time has no passcode set. It is possible to have limits with no passcode, which makes them reminders rather than limits.
Settings, Screen Time, Use Screen Time Passcode. If you set it yourself, you already know the ceiling on how much it can do.
If it is a third party blocker that went quiet
Check whether its Screen Time access is still granted, in Settings under Screen Time. Access can be revoked, and most apps have no way to tell you loudly when it happens.
This is worth knowing before you choose one. Ask what happens when its permission is pulled. If the answer is that it stops silently and nobody is told, the app has told you how much thought went into the parts that matter.
Common questions
Why did my Screen Time passcode stop working?
Most often it was reset through the Apple Account recovery flow, which is available to whoever controls the account. That recovery path is deliberate on Apple's part and it is the ceiling on any passcode based setup.
Does restarting the phone clear Screen Time limits?
No. If limits disappear after a restart, they were removed rather than suspended, and something or somebody removed them.