From what you've provided, it sounds like your monitor has failed. There are a couple of points to consider though:
Are you using the same cable between the potentially faulty monitor and your other monitor? If not and it's possible to do so, use the same cable for each to eliminate this being the problem.
Are you using the same port between the potentially faulty monitor and your other monitor? If not, it's possible something is wrong with the output to that port, which is possible if they are different technologies (VGA vs DVI vs Display Port vs HDMI).
If you are using the same cable, in the same port, but with a different monitor, and that scenario works, then your original monitor has failed. There isn't a viable repair strategy for monitors, parts are hard to source and new monitors aren't typically too expensive.