1. The title is missing
Title is required. It is the easiest field to skip because the limit values feel like the real content.
2. The feature is not on your plan
Bulk metafield limits, variant metafield limits, Advanced Rules and multilingual messages are Premium. Locked features are marked rather than hidden, so the form may look available while refusing to save.
See plans.
3. The store is at Shopify’s ceiling
Shopify allows 25 active validation functions per store, counted across every installed app.
To free space: disable rules you are not using, consolidate several limits into one rule, or check what other apps are holding. See limits.
4. Nothing is selected
Product and collection limits need products or a collection chosen. A limit type enabled with no target and no value will not save.
Verify the fix
Save with the status enabled, then test a cart that should be blocked. Saving is not the same as enforcing.