When removing a lead from a Smartlead campaign, the "removal failed" error can occur for several reasons:
1. You might be missing required information - both Campaign ID and Lead ID are mandatory fields for this action.
2. The lead might be blocked in your account, preventing removal.
3. The Lead ID might be incorrect - ensure you're using the ID from a Lookup Lead in Campaign action.
If you continue experiencing issues, please request human assistance by clicking on "Talk to a person."