Key FOB program w/aftermarket alarm?

[Loco5.0]

Bought my '96 Cobra w/an aftermarket alarm already installed. I replaced the batteries in my key FOB today (OEM key FOB) and now it's not working. I tried the flip the key on (not start) then off 7-10 times & that didn't do anything.

Any tips for me?

 

[BlownFiveLiter]

What brand and model alarm? The on/off method is only for the factory keyless entry.

 

[Loco5.0]

Bought the car w/it on there. Hornet 700T. DEI support is useless. I couldn't get anyone & had to leave a vm.