1997 Jetta Alarm Issue

My Son Just Bought A 1997 Jetta. The Previous Owner Dropped It Off And It Was Fine. He Got In And Tried To Start It. It Is Manual Transmission. It Was Cranking When He Tried It Originally, Now Everything In Car Works But There Is Nothing When You Turn The Key. We Checked The Batttery But It Is Fine. Also Starter Good Too. When We Tried To Jump The Alarm Went Off. We Tried Resetting Alarm By The Door As Suggested But Still Nothing. Any Ideas??? WE WERE ABLE TO PUSH START IT AND IT RAN FINE, BUT AS SOON AS WE SHUT IT OFF WE CANT RESTART IT. THE ALARM BLINKS ON THE DOOR WHEN YOU SET IT AND THE RADIO AND DASH ARE ALL WORKING FINE.

open the trunk on the driver side (or maybe passenger side) pull back the carpeting on the side and look for a styrofoam box, open it and unplug the module and see if it fixes the issue