PS4 Powers on, beeps 3 times and then powers off

Hi everybody,
I was wondering if somebody could help me. I was playing on my ps4 for 10 minutes when it suddenly switched off (without the power down sequence) I thought there was a power cut in the house. So I turned the ps4 back on to see if it would happen again, after booting up call of duty warzone, the ps4 turned off again.
I decided; thinking it was overheating, to open it up and clean out all the dust which I do every couple months. Baring in mind my ps4 has sounded like a 747 for the last 2 years or so.
after stripping down everything inside the ps4, cleaning it carefully and putting it back together (without reapplying thermal paste) the ps4 now won’t turn on.

I’ve double and triple checked all connections, the ps4 beeps once, the fan starts for a second, then ramps up really loud, then beeps 3 times and shuts down.

Does anybody know why this is, and if I was to buy thermal paste would this solve the issue ??

Thermal paste is huge. It’s gotta be on there. Also make sure that all of the ram chips have their thermal pads on.

Did you clean on the heatsink?

Make sure the fan is properly connected. Inspect the cable and connector for the fan. Be sure that’s intact.

Three beeps ah memories not good ones either more like classic hair pulling ones it is the classic sound of a screwed apu