Doorbell constantly drops offline

My ring doorbell (battery doorbell plus) worked perfectly for a month - I purchased a plan before my trial ended so was all set but now it just drops offline constantly. Have followed all the advice on resetting it, moving router etc but it lasts a few mins then drops again. Can’t see why it would go from working perfectly to not at all and it seems strange it happened around the time my trial would have ended. Would really appreciate anybody’s advice as it’s useless to me how it is. Thanks!