This has come up occassionally in our office, where the PDF option becomes unavailable. We simply re-install the PDF Converter (Program Files\Graphisoft\ArchiCAD 10\PDF Converter\Install) on that machine and all is well. I'm not sure if this is the best way to remedy the problem, but it works for us without incident. Did you try to re-install the PDF Converter after following the steps in the attached link?
MacBook Pro 2.4 GHz Intel Core i9, 32 GB of RAM
AC25 US (3011) AC24 on Mac OS Catalina 10.15.7