I stumbled across this thread Post code bits meaning which has a link to a github file with code definitions but cannot confirm that it also applies to the Ryzen mainboards.
I am having the exact same issue but I am using a 2x16GB 5600 MT/s kit (Crucial CT12K16G56C46S5). Even tried a single 4800 MT/s SODIMM. All 12 system checks are green followed by a 0xA3 post code (BGBGGGBB). I would still contact support with your post code before trying to return your RAM since getting a 5600 MT/s kit isn’t guaranteed to work.
EDIT TO ADD:
Or if you do end up returning the RAM then get something on the official support list. Reading around there have been reports of the kit I got working. But probably safer to get something framework has verified to be compatible.