iPhone can only block about 50 apps (and about 50 websites) at the same time, counting everything that's active at once. If you go over that, iPhone may stop blocking them. Bring the number down, then open Slow Time Club.
What counts towards the 50
Every app you picked one by one in:
a running Quick Block
any Focus Sessions running at the same time
App Limits whose apps have used up today's time
A whole category, like Social, counts as one item.
How to get back under it
Use categories. In a Quick Block, Focus Session or folder, pick a category instead of choosing every app in it one by one. App Limits only work with single apps, so this doesn't apply to them.
Remove apps you rarely open. Keep the ones that really pull you in.
Split things up. Spread apps across Focus Sessions that run at different times instead of one big block. For App Limits, you can put some limits on Weekday and others on Weekend, so they don't all apply on the same day.
Open Slow Time Club afterwards so it puts the right blocks back up.
App Limits have their own caps to help with this: up to 10 apps per limit and up to 5 limits.
If blocking still isn't working, go through Blocking isn't working: start here.
Why this happens
This is Apple's limit on how much one app can block at a time. It covers everything Slow Time Club has running together, not each block on its own. When you go over it, it can look as if blocking just stopped. Sorry about that.
Related: What are App Folders and how do I use them? · App Limits: how do I set a daily time budget for an app?
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