I moved my Photos library to an external drive due to it's size. I removed ~/Pictures/Photos Library. When I launch Photos it asks to choose library. I select "Other Library" and traverse to external drive where I select the photo library I moved. Everything works as expected. I then choose Photos preferences and and select "Use as System Photo Library".
The next time I launch Photos it cannot find the library and I have to go through the above sequence again. I removed ~/Library/Prefernces/com.apple.Photos.plist and redid the procedure above. When I check com.apple.Photos.plist it has the path to the external library. Yet when I launch Photos it again says it can't find ~/Pictures/Photos Library.
Any recommendations what to try next?