The backup cannot be performed because '%1!s!' was requested after the media was formatted with an incompatible structure. ...

The backup cannot be performed because '%1!s!' was requested after the media was formatted with an incompatible structure. To append to this media set, either omit '%2!s!' or specify '%3!s!'. Alternatively, you can create a new media set by using WITH FORMAT in your BACKUP statement. If you use WITH FORMAT on an existing media set, all its backup sets will be overwritten.