For 2012 or earlier Mac Pros which aren't fixed by a standard SMC reset, use the SMC reset button on the motherboard...
Shut down. Unplug the power cord. Open the Mac Pro side access panel. Just below the drive 4 sled and next to the top PCI-e slot is a small button labeled SMC. Press and hold it for 10 seconds. Close the side door. Reconnect the power cord. Wait 5 seconds. Start the Mac normally.
Also try a PRAM reset, if this doesn't help.
I usually write a blog post about once a week. The latest post can be viewed here: We Need Trump and Musk: I wonder if Trump and Musk might like to visit here after they have finished sorting out America! (posted 2025-02-11 at 11:40:37). I do podcasts too!. You can listen to my latest podcast, here: OJB's Podcast 2025-01-30 Pragmatic Libertarianism: Freedom is important. Maybe it's all that really matters..