I moved my photos library to a new external hard drive and a now can not open photos with new or old library!!!
Following the procedure from the Apple website, I copied my photos library to my new external hard drive and tried to launch photos with the option key held down. I responded to the question to pick my library and it did not work. Further more, now I can not launch photos with my existing local library file! I'm dead in the water. I'm running the newest version of macOS Catalina on my iMac.
iMac Line (2012 and Later)