R7525 Stuck in "Please wait while the system is initializing."

Recently purchased a used R7525 that did not come with CPU or memory. We initially put in dual EPYC 7543 with 8 x 16GB - 2RX8 DDR4 for each CPU, to find that the system had not been updated to support Rome CPUs. We got a EPYC 7272 to upgrade the bios and firmware, placing the CPU in the CPU1 socket, and a single stick of memory in the A1 slot. On startup, the iDRAC light blinks yellow, with no other indicator lights lit up, and after it gets through "Initializing and Verifying System Security", the system gets stuck at "Please wait while the system is initializing...". We've tried letting it initialize for over an hour, as well as setting the jumper to reset NVRAM, with no success.