Domain transfer from Bluehost not working


I would like to transfer my domain from bluehost to Cloudflare.
I unlocked the domain at bluehost and requested the EPP code.
This I inserted at the fill in transfer sheet.
I get this error message:
The registry has indicated that the authorization code is not correct. Please re-enter the code again. If you continue to receive an authorization code error, please request a new code from your current registrar.

I tried several times. The domain is older than 60 days, so no problems should be with that, right?
Any ideas what is going on?
Thank you very much for help.