Mac mini not turning on after upgrading the RAM

Hey guys! I have a problem. Since I needed more RAM at short notice for a program for college, I've decided to upgrade the RAM by myself, because that looked relatively easy in all tutorials. So I ordered 32GB RAM in a set with the iFixit tools and took my time yesterday afternoon.

Unscrewing everything worked great. Wifi antenna, fan, status LED, power connector- everything was easy to remove. The two big screws holding the motherboard in the case were my only problem, they were really tight and I tried to get them out for about 15 minutes. Unfortunately I slipped off one of the screws (see picture) and thought this doesn't look like critical damage to the logic board. I then installed the new RAM, reassembled everything, and the Mini wouldn't turn on. Nothing at all.

I know a little bit about PCs, asked in various forums, talked to several people who know better, but I just can't find the fault. The Mini seems to get absolutely no power, the status LED does not light up, the fan does not turn on and the USB outputs give no power.

First of all, I would like to know if I have seriously damaged anything with this scratch. Everyone has told me so far that this can't be the case, because the Mac can't suddenly lose power from such a scratch.

Here is everything I have already done:

• Disassembled and reassembled the Mini for 5h about 20 times.
• Checked all cables. It can't be the cables, no cable is damaged and all cables are seated correctly when reassembling.
• Also re-installed the old RAM bars about 5 times (in a different order also). The RAM-Chups are also definitely sitting correctly and not too loose etc., so it can't be because of that either.
• Checked the small ribbon cable of the power button. On Reddit it was assumed that the Mac can not be switched on at all, because the cable was damaged during disassembly. It is definitely correct and is not damaged.

I'm really don’t know what to do. I only have 3 guesses, but they are relatively unlikely:

• My power cord has suddenly broken, but this can not be i think, because it was working normally before.
• I damaged something by electrostatic discharge during disassembly. But that can't be also, because I did the whole thing on an appropriate mat, was grounded and didn't play around with the screwdriver anywhere.
• The scratch is so bad that I have completely broken something. But that wouldn't explain why the Mac doesn't get power anymore.

I would appreciate any new ideas that I haven't had on the screen yet. Thanks and have a nice day!