On 30 AMP service with a EMS system. I can run 2 13,500 BTU Coleman PS AC's at the same time. OEM rear AC was a 11K unit. But I replaced it a couple months ago.
I don't need to run the 2 AC unless outside gets above 90º.
OP check at your generator for a tripped breaker. You should have a 30 AMP & a 20 AMP one or at least 2 20 AMP. Your AC wiring should be split between the 2 breakers. And should allow both to run the same time on the generator.
Without a EMS service you will not get both to run the same time on shore power.