Buildapc

Hello, I have been trying 2 small ff PCs, one HP Z2 mini G9 (i7-13700) and one Lenovo P360 ultra (i7-12700). I decided I will keep the Lenovo, but though I might as well keep the more recent CPU.
After the swap, the HP booted fine, but the Lenovo didn't, the fans spin for a second then off. It never gets anything on display.
I though I had screwed up while doing the swap or reassembly, so I took off the CPU again, checked there was no damage, put it back with fresh paste again, still no luck.

I am aware that both CPUs manage different Max ram speed (4800 vs 5600) so I tried to swap, or leave just one module, no luck.

I though I fried the CPU somehow, so swapped back to each their own, and all works.

Both sockets are LGA 1700/1800 as far as I can tell. Both power supplies are identical, both CPUs are the 65w tdp versions (ie not the T or K versions). The only difference I can see is that the 12th gen is vPro, 13th isn't. Both BIOS were updated prior to the swap.

Am I missing something? Thanks for any advice.

PS. Both machines came with an nvidia t1000, and I tried with or without in case it was a power draw issue, it doesn't seem so.