Please refer to this page for the list of supported repositories for the SQL plug-in. Also, please check the access permissions on a backup repository.
If everything is configured as described in the user guide but the issue still persists, please contact our support team and share a case ID for our reference.
This type of storage cannot be used as a target for SQL plug-in backups, you may open the link that I shared in my previous post to get more info about the supported repositories.
The error message on this screenshot says about a helper appliance that must be configured in the repository settings.