While the procedure will vary with the jurisdiction, if an at-sea vessel finds their VMS is not working and they cannot fix it, they may be able to contact the FMC and get permission to continue the voyage. If they do get such authorization, they may get an inspection when they return to port. The FMC may also order them back to port. It is unlikely they will be allowed to leave port again without the VMS being repaired, so that they may need 24/7 VMS technical services at their home port.