Motherboard output works but GPU output doesn't

My computer has recently started to not connect to my monitor. I get the dreaded no signal. After a bit of Internet research and experimentation, nothing solved the problem. I then decided to test if my GPU might be the problem. I connected my monitor to the motherboard via HDMI and sure enough, I get video. Everything seems to work fine. Tried it with a DVI between monitor and motherboard and that also worked. Obviously connecting through the graphics card is preferable. Any help or advice please? Thank you.