It's been 3 weeks since the buyer has bought my RX 5700 XT (used for 3 ½ years and worked when I last used it like 2 months ago and then kept it somewhere safe where it wouldn't be damaged.) and for the past 2 weeks, a dispute has been ongoing, as the buyer claims that the GPU isn't working (1st time they had a 500W PSU in combination to an i5 9400, which then I told them to change it to 600W and above).

Second attempt was them trying a 650W PSU and still no luck. I asked them to send me proof via video...and based on my own knowledge, the GPU can't be causing that right? The inability of the whole PC to start up?

Therefore I've asked them to send another video of them attempting to start the PC with their previous GPU.