Electrical, alternator replacement

I just replaced the alternator in my car listed above is 250 because the battery the car kept shutting off and the electrical systems were fading out quickly after jumping the car. The battery was tested as good (although I’m suspect).
No issues getting the alternator removed and reinstalled with a new unit, however, I can’t get the car to start, even with a jump vehicle attached. The windows, door locks, power seats, windows radio and climate control do not even turn on, only the main dash cluster. I’ve replaced the fob battery and when I hold it up to the start button, with the brake depressed, the light on the push button start never turns green. I can hear nothing from the engine high makes me wonder if it is some sort of immobilizer that I haven’t been able to get past.
I’ve held down the start button it’s key next to it for 30 seconds, I’ve held down panic key for 5 seconds, locked all the doors and then unlocked the driver door with the key shank, unhooked the neg battery cable for 10 minutes, none of which are allowing me to start the car. I have checked the fuse linkage and fuses and double checked the alternator hookups. The only other common thing I’ve read is that the battery might be bad.
Out of ideas please advise. Thanks