2017 iMac not recognizing external monitor

Update on this problem: I have been able to narrow the problem down to the 2 Thunderbolt 3 ports not functioning. With further research, I've found that this problem appears often after updating the OS to Monterey. That is what happened with my system. I had been running Mojave on my system, and all of the ports worked fine. Upon updating to 12.0.1 Monterey, the externals I had been using via the Thunderbolt 3 ports became inaccessible. So it seems that this is an operating system problem. The most recent effort to find a solution with Apple Support resulted in several advisors suggesting the same fixes, such as resetting the SMC and NVRM, none of which have helped. I have since updated to 12.1. The last advisor I spoke with has advised that the only other thing they can suggest is to try reinstalling the operating system, which I have not yet attempted. I have been trying to resolve this situation for almost 6 months now and I am getting the sense that Apple advisors don't have a solution.

Thank you, @bbesspete. My iMac is not a version with the Apple T2 Security Chip, that I know of.

I have powered down the device, removed all of the cables and replaced them, attempted to detect the monitor through System Preferences. The failure to detect external monitors began after updating to Monterey. I have also noticed random and intermittent issues with the Magic Mouse and keyboard not being detected since that OS update. In these cases, I have had to use a mouse attached with a USB cable or attach the power wire to the keyboard and mouse, which seems to "wake up" the iMac and it detects them again (this happens even when they are fully charged).

Any suggestions would be appreciated!