Help Needed: Brother's PC Monitor Not Displaying Anything

Hello everyone! I have a question on my brother's behalf and I'm hoping someone here might have the answer and solution we need. So here's the issue: his main monitor is refusing to display anything from his PC. Frustrating, right? Now, the weird part is that the monitor itself appears to be receiving power as it lights up just fine. To troubleshoot, I even connected my own monitor to his setup, and guess what? His PC recognizes the monitor as plugged in and connected. Surprisingly, both my other brother and I have no issues with our monitors on his PC (and all cables are in good condition). But unfortunately, my brother's monitor just won't display anything on any of our PCs. It's an MSI Optix MAG241CR, and it's his 18th birthday today, so it would be really disappointing if his new monitor had to be his main for now. We would greatly appreciate any help or advice. Thanks!