I'm having the same problem, and it's frustrating. Cmd + ` works fine in every other app; I use it constantly. But @Brendan Murphysays it works fine for him, so I wonder what could be different, if we're both running the same version (I assume). I have 10.5.7 with Catalina, Mac OS 10.15.7--maybe it will be fixed when I upgrade to Big Sur? (I need to wait until the IT people at work give the OK.) I already tried trashing the app (which I think is the same as "uninstalling") and re-downloading and installing from the Mac App Store. No effect.