I tested the GPU before I buy. I get it from someone I know. The condition shocked him as much as it shocked me. We are trying to figure out why it happened
High Power 750W Astro Elite PSU
PSU is one option what might have happened.
Your PSU, while it reviewed well,
link:
https://www.techpowerup.com/review/high-power-agd-750/
It did came out in 2013. That's quite an old platform, 8 years old as of today. It is possible, that your PSU sent too much (or too little) voltage to your GPU, frying it. And PSU only came with 5 years of warranty. With this, your PSU is long past it's "service life".
Though, for conclusive testing, put RX 460 into 2nd PC and look if you get any video signal there. If you don't, it's safe to assume that GPU is toast.
You may try all 3 video output ports as well. Since sometimes, when HDMI or DisplayPort doesn't want to show a pic, you could get some life out of DVI.