Bought a pc today second hand won't boot up

I bought a pc second hand and got it today, the sender sent it with the GPU taken out, I assume so it doesn't snap anything.after putting it back in and booting it the fans spun up on the GPU CPU and the 2 others but the ram doesn't light up and there is a yellow light on the pciex16_1_led and there is no visual output to a screen. Please help

(GTX 1660 Super, Ryzen 5, 150016 Go RAM, prêt à jouer. Alim Be Quiet 650 W, SSD250 Go, boîtier gaming avec ventilateurs LED) This is what thé seller had written in the bio. If someone could help me solve this or let me know what I should do I've got 3 days to solve or send back