Second monitor on iMac and MacBook Pro are black

I have 2 24" Apple Cinema Displays that I have had for a while. I use one as a second monitor on my 2014 iMac and the other for my 2015 MacBook Pro (I really only use this on set). They have been reliable monitors so I haven't needed to replace them. I recently started having problems with them. I noticed on the iMac that the second monitor seemed dim and then it eventually went black. I swapped the other one in and everything went back to normal for a while. Now both monitors are black when connected to both computers. The thing that is confusing is that both computers think the monitors are connected. A drive I have connected through the USB on the monitor still works fine and the Display settings in System Preferences lets me arrange them.

They're old so maybe they finally need to be replaced but this seems like there is a fix that I'm missing. Bad cables? It could be bad ports but I doubt that both computers at the same would have ports go bad.

The iMac is running Catalina and the MBP is running Big Sur.