Linux Mint 20.1 (Cinnamon): Changing Desktop Backgrounds

I changed the background on our laptop FROM Bookwood 4000x2251 TO Sele 3840x2160, via Menu > Preferences > Backgrounds.

I have now decided that I really like Bookwood 4000x2251 better; however, when I click on Bookwood 4000x2251, then restart the laptop, the background doesn't change! Arrggghhhh! What am I not doing correctly?

Thanks for the help, guys.