Question Pc starts but no display, keyboards and mouse not lights up

[Griwen]

So, I replaced my old psu(still works good) with new one and my pc starts, all fans are turning, but i have no display and my mouse and keyboard light isnt turning on. my pc works good with old psu and i thought the new one psu was the problem, i went to the shop and they gave me a new one( we tested it there too). But even with that psu, my pc only turns on but still no display, etc.
My specs
Ryzen 5 2600
XFX RX 580 8gb
G.skill 16gb
1STPLAYER 750AR psu 750w 80+ gold (new one) //////// aigo gp550 550w(old one)
Gigabyte B450m ds3.h

 

[rgd1101]

we tested it there too)

tested on your system?

are the modular psu? using only the cable from the psu?

 

[Griwen]

tested on your system?

are the modular psu? using only the cable from the psu?

no psu was tested on another system and its not modular. could it be a gpu problem ? but everything runs perfect with old psu.