Is there any fuses added to the car for the remote starter/receiver? Maybe since it's likely a parasitic load on the battery the fuse blew when the battery was changed. I know some cars you have to do things like key in, "ON" position and then press the brake X times and then "OFF" or something to that effect. Check for fuses and make sure that it's all still hooked up, possibly the receiver was just unplugged from it's power supply and if you still have nothing I'd try looking for a "contact us" link on their website.
93 EH3 Si Hatch JRSC'd @14 psi - 1st car, 8yrs, never forgotten
91 DB1 LS B20v Xsi trans -DD and track duty
87 CRX Si - Summer toy
97 Odyssey - Family stuff