UPDATE:
I contacted Jim, outside of the Forum, so that we could work through the problems that he was facing with getting the BIOS updated to the latest version so that he could run his Ryzen 5600X. These are the steps we undertook, to sort out the problem.
Attempted to clear CMOS but ran into issues with it not clearing properly. So removed motherboard battery overnight.
Stripped PC down to basic components, CPU, GPU, 1 stick of RAM, 1 monitor, USB keyboard and mouse.
Fitted new CMOS battery
Started PC, CMOS had cleared (having been left overnight) and was then able to enter BIOS.
Shutdown PC refitted NVMe drive, restarted PC and booted into windows.
Updated chipset drivers rebooted PC. Once back into Windows restarted and went back into BIOS
Updated BIOS to F40 using QFlash.
Rebooted to Windows, all OK.
Restarted PC, back into BIOS, updated to F61 using QFlash. Rebooted to Windows, all OK
Shutdown PC, disconnected from mains power, replaced 2600 CPU with 5600X. Restarted PC all OK.
Shutdown, disconnected from power supply, refitted all components.
Restarted PC, all now functioning as expected.