Fix
Short answer: The form still refers to a field that was deleted or had its type changed, usually inside a lookup or aggregation field. Remove the broken reference and go live again.
Why it happens
- A field was deleted or changed type, but a lookup or aggregation field still uses it.
- The form can't find that field, so it can't render or submit.
How to fix it
- List recent edits: fields deleted or retyped before the last go-live.
- Open each lookup and aggregation field. Remove any configured field that no longer exists.
- If a lookup still fails, reconfigure it from scratch.
- Check that field dependencies don't contradict each other. Also check that mappings, required settings and step permissions fit together.
- Click Edit process > Go live, then create a new item to test.
- Try the process in an incognito window to rule out the browser cache.