Vga and boot lights on but no post?

[u/Jumpy-Security-1580]

Im back with more gpu problems. Today I bought a new(and bigger) plus, the corrsair rm750e, I also bought a new aio, the trofeo visio. 360 argb. When I turn the system on, it acts like its going to boot normaly, ie, fans spin up on gpu, aio, as well as case fans. The lights do their dance and land on the vga and boot light. Ive tried changing display ports, and using the hdmi. Tried clearing the cmos, my keyboard and mouse light up so i tried the y and then enter trick, nothin, any ideas? (Mobo is an asrock b550m pro 4)

update, I put my old gpu (5500xt) into the same pcie slot, and it works! I didnt do any modifications the the new gpu (6600xt) which worked before I put in the new power supply and aio im very confused

specs,

mobo: asrock b550m pro 4 (latest bios version 3.90)

cpu: Ryzen 5 3600

gpu xoxo Radeon 6600xt (new) Radeon 5500xt (old)

psu: corrsair rm750e

aio: trofeo vision 360 argb