Help pc wont switch on

Hello all after a long time just today I opened pc to clean it I just took cpu out put new thermal paste putted back and now my pc just starts it turns on for like 20 or 30 seconds and it turns off and it keeps doing that but there is no display aswell all fans running gpu aswell power supply...

G.SKILL Ripjaws V Series 8GB (2 x 4GB) 288-Pin DDR4 SDRAM DDR4 3200 (PC4 25600) Intel Z170 Platform / Intel X99 Platform Desktop Memory Model F4-3200C16D-8GVKB I purchased the above ram, and my current setup is as follows: CPU: AMD RYZEN 7 1700 3ghz 8 core Motherboard: ASUS prime b350-a micro...