You have hit the rate limit. You can easily find the answer in the following equivalent threads:
- Too many certificates already issued
- Too many certificates already issued for: startdedicated.de
- Too many certificates already issued for: myfritz.net
- Too many certificates already issued for
Removing a certificate will not reset the limit. You have to wait for the limit window to expire.
Also note that for testing purposes (assuming you may have issued several certificates because you were testing the service) you should use staging.