You’re pretty much describing the process i went trough, with some altered details. Power outage fried my HDD, ended up replacing it. Suddenly monitor doesn’t work after reconnecting it. Tried the DP cable i had lying around, tried the 2nd HDMI port, both with the same HDMI cable and a different one. Tried a different monitor. (i don’t have a 2nd system I could hook my monitor to, but at this point I’m fairly sure it has to do with the HDMI port of the GPU which I simply don’t have the funds to replace… Might have a guy look at it, maby he knows something I don’t)