Thanks guys, it seems to be somewhat intermittent which makes it all the more frustrating..

I had to unplug the trickle charger after 12 hours or so because the car was outside and it was suppose to rain overnight. The charging light on the tender was still on red which indicates it was still charging and not yet at 80%. The car sat overnight, went out the next morning and started it with no battery light. Left it running for an hour, still no light... was hoping this would help with the theory that the alternator just hadn't had enough time to recharge the battery.

This morning started the car and the battery light is back on.

So I'm assuming the battery still hasn't been charged to full and/or there is in fact an issue with the battery even though Autozone read it as "good"... Or its the alternator... Is there a way to test the alternator at home (without a volt meter)? Starting the car and taking the terminals off the battery or something?