APB is 32-bit and RTX cards aren't compatible with 32-bit systems/programs. This was also stated by Matt on Q&A with Kempington.
"I'm well aware, unfortunately, of the memory issues. The RTX issue in live is kind of complicated because the live game is 32-bit and Nvidia's drivers for the RTX cards it's just ... The driver is part of the problem, it's not that backwards compatible and then there's problems on our end because the engine is so old. From what I can tell the RTX cards work beautifully in the new engine. We haven't had any reports of Out of Memory issues or crashes or anything like that. In general there are a number of situations players find themselves in where they do get an Out of Memory error or crash in the current engine that won't happen. That's exclusively because of the jump to 64-bit addressing memory and things like that. - Matt Scott"