> What does it mean to put a scheme in a cname?
It means that https:// shouldn't be mentioned in the DSN records
> How can I solve the problem?
You should edit your DNS records and remove it
It means that https:// shouldn't be mentioned in the DSN records
> How can I solve the problem?
You should edit your DNS records and remove it
So a user who copy pasted from the URL bar into the DNS records (probably following some guide) ended up with the wrong thing in there.