In order to access the referee app, you must have reregistered as a referee for that season via the WRU Game Locker.
If you have registered as an unattached referee, then a club will not need to approve you and you will automatically regain access to the referee app.
If you have registered as a senior referee with a club, then the club will need to approve you, but you will not be required to complete a DBS application. Once the club approves you, you will regain access to the referee app.
If you have registered as an age grade referee, and you do not have a DBS, or your current DBS expires within 90 days, then you will need to complete a new DBS application and have that returned before your club can approve you. Once the club approves you, you will regain access to the referee app.
You can register as more than one of the above, e.g. as a senior and an age grade referee. Each scenario will still apply however.