If the ignition switch was turned-on at any point while the electrical connectors at the base of the seat were disconnected, then you will get an SRS fault message on the instrument cluster - is this what you are seeing? If so then it will need clearing with STAR computer (or other SRS reset tool). Otherwise, the seats you fitted might not be the same as the ones removed (e.g. half-electric, full-electric, memory seats etc) in which case you will need STAR computer to tell the car that it now has different seats.