Question!!!

In your OP you mention you only run intrastate in AL. Which suggests you don't have federal interstate authority (FMCSA MC number) or apportioned plates. Probably no IFTA account either.

What it sounds like is: you have regular plates and you can't "add states" to those. In most states the apportioned plates actually look different than the car tags and have the word "apportioned" printed right on them. Not exactly sure about AL, so maybe someone else from there will be able to describe in more detail. With regular, non-apportioned plates you can go in/out of other states by buying trip and fuel permits. My Dad does that when he needs to take his Kodiak/flatbed out of GA. Not sure if that's possible in case of working in GA for weeks at a time.

You could check the Georgia Trucking Portal, or just call someone at that office (a division of the dept of revenue) and ask. Another option would be to call the GA MCCS enforcement division (diesel cops) and ask them what you ought to have, given the scenario you describe. Since AL is right next door, I'm sure they get that question or write a few tickets to people that don't ask until caught.