Can’t get past bios after swapping over CPU

So I got hold of a 5600x recently, upgraded the bios on my MSI B450 Tomahawk Max to the latest (v39) version, installed the new chip...and I can’t get past the BIOS screen now. The chip is recognised, it just won’t boot windows, every time I try to exit BIOS it just reboots to back to the BIOS screen. Replacing my old 2700x makes everything work fine. Anyone know what I need to do?