Unable to use Photos Events as Sceensavers on My External Monitor in Tahoe

24 inch M1 iMac with 27inch Dell 4K external monitor. Since switching to Tahoe I am unable to use my Photos Events as screensavers on the external monitor. The Wallpaper settings for each monitor setting cycle as desired but I am only able to set my Photo Events as a photo wall screensaver on the iMac. The same settings for the external monitor only results in one of the Apple dynamic screensavers. I can't even change that to a different dynamic screensaver. I wandered through the screensaver .plists and found no intuitive ways to fix that. Any ideas welcome.