Cannot add Apple photo library on external drive

I followed the instruction here step by step (including giving all the necessary permission as required by Big Sur) to add my Apple Photo Library that is sitting on an external SSD. However, the library is seen as greyed out and cannot be added. Any idea how to resolve this?

Make sure Apple Photos has the library set as the “System Library”. In Apple Photos, open the library you want to use in Mylio, go to preferences, general and select “Use as System Photo Library”

yep, done that already, but the photo library file still greyed out

Ok. so to make sure we’re on the same page the button inside the yellow oval bellow shows greyed out for you?

(Since you made the external drive library your System library, there’s no need to navigate to it, just push the big Apple Photos button)