Lost External Display Menu Bar After Update to MacOS 12.5

Updated my 2017 20.5 inch iMac to MacOS 12.5 yesterday. Now my external AOC 4K monitor no longer displays the menu bar. Have tried deleting the com.apple.windowserver.plist without change. The external monitor is driven by a thunderbolt to displayport cable. Unplugging and replugging the cable had no effect. Windows moved from my iMac to the external monitor are still linked to the menubar on the iMac. Previously the menubar on the external monitor reflected that of the active application on that monitor. Anybody else have this problem?