Question GPU not displaying but Motherboard did

[Setiyok]

So I just bought used Zotac GTX 1050 single fan.
I tested on my own rig, spec:
Asus ROG Strix B550-F Gaming (Wi-Fi)
Ryzen 7 5700X
32GB Memory
It works perfectly fine even run Furmark.

The next day, I planned to give it to my brother with his old computer, spec:
Gigabyte H61M-S2P
Intel i3 2100
4GB Memory

The GPU fan is spinning, but there is no display, but when I connected to motherboard, it did display, when I checked on device manager, only microsoft basic adapter shows even the GPU is on.

Any idea how to solve this?
I tried on another old computer which only has intel G630, it did work perfectly.

Thanks in advance.

 

[RaidHobbit]

I`ll assume its not a very low power PSU.

Plug the GPU in but connect the monitor to the onboard graphics. Head over to device manager, double click on the GPU, and have a look around to see if any errors are listed in the status window or if the GPU has been disabled. If its disabled, enable it, and switch the cable to it. If there is a status error then please post it.

Other issues may be its not seated properly or its cables aren`t plugged in correctly. Disconnect, reconnect, try again.

 

[Setiyok]

I`ll assume its not a very low power PSU.

Plug the GPU in but connect the monitor to the onboard graphics. Head over to device manager, double click on the GPU, and have a look around to see if any errors are listed in the status window or if the GPU has been disabled. If its disabled, enable it, and switch the cable to it. If there is a status error then please post it.

Other issues may be its not seated properly or its cables aren`t plugged in correctly. Disconnect, reconnect, try again.

Thank you, it's solved now.
I reseat it but clean it a little bit and there is some rust on the pin, and I scratch it with my finger nail.
And I blow the pcie slot.