The requested vessel with name SAN SEBASTIAN and MMSI:0 and IMO:5310474 is temporary not in our database.
Perhaps you mean one of the following ships:

Vessel name IMO MMSI In range Destination Last report
SAN SEBASTIAN 9363314 636017555 YAWATA Feb 22, 2018 23:00 UTC

Also, you may try to find the vessel in our comprehensive Vessels Database or track this ship on the map.