I was gaming for probably 2 years with PC connected to Samsung tv, then about 6 months ago it decided to stop working for me for whatever reason. Nothing wrong with the computer at all, just took it to my buddies house the other week and the HDMI worked perfectly fine connected to his computer monitor.
No idea whats going on here with the TV, xbox streams to the tv just fine however. Tried unplugging and replugging everything to no avail.
Try changing the order you boot the PC and select the input on the TV it's connected to. That affects the handshake between them. If you get it working again it might go back to working as it did before. HDMI can do some weird stuff.
Try a different HDMI input.
Try a different HDMI cable.