if you replaced your HDMI port yourself, which got it working, then it stopped working again, it could very well be that the HDMI port either went bad, got damages, or pulled a pin off the board.
if you have good experience with soldering, Attach anotherone yourself. if you dont solder often, i suggest getting it repaired through a store.
if the HDMI port doesnt fix the issue, run through a reflow on the GPU. This may getit working.
if it continues to fail, then you are looking at a board failure. in this case, replacing the device is your best option.