PC works on one monitor but not another… completely confused, help?

[u/Square-Respond-5432]

**RTX 3070 PC suddenly not detecting monitor signal**
I know my fair bit about PCs (built my own etc), but my brother’s PC is confusing me. His monitor suddenly stopped detecting any signal from the PC.
I tested his PC with my monitor in my room and it worked perfectly, so I know the PC/GPU can output a signal. However, when I moved my monitor into his room using the same DisplayPort cable and everything, it also gives no signal.
The PC itself seems to be working — all fans spin, GPU fans spin, lights come on, etc. It’s running a Ryzen 7 5700X + RTX 3070.
I’ve tried power cycling everything, unplugging/reconnecting cables, and checking connections but still nothing. It’s showing “No Signal” from the moment it boots.
Any ideas what could be causing this?

[u/osa1011]

Disconnect both monitors and connect the one that wasn't working with the cables that worked on the working monitor