Could not access Apple Photos Library

Hello - I am trying to move my Apple Photos Library which is very large (80 gigabytes and 20k photos) to Lightroom.  I had to upgrade the Mac OS to Catalina which has really slowed down the machine.  I tried to 'Prepare Apple Photos Library for Migration' steps by selecting library as System Photo Library and then started the migration in Lightroom. The problem is the process never finished -- I let the computer sit there for a week and it froze and never recovered so I had to hard reboot.  Now I go back in and try the process again and it says "Apple PHotos Library is Missing or Damaged" or "Lightroom does not have correct permissions"....  I opened the Photos Library on the Mac after the re-boot and I can navigate it fine.  How do I fix this so I can re-start the import?  I am trying to preserve a complex scheme of folders and albums I have in existing Photos library.