Photos not working on Mac
Long story, I'll try to be brief. I recently switched back to an iPhone 12 after having a couple of Pixels... All my photos from the Pixel phone were shared vis Google Photos and Google photos on the Mac. So instead of having Google photos and Apple Photos I just decided to go with the native application. Photos are sharing fine on my iPad, Macbook and phone but not on my iMac, I did have a really old iPhoto library on an external drive which I then sent them all to Lightroom. Now I cannot open Photos (no library) nor can I select Photos in the iCloud section of preferences. How can I get my phone photos on to the Photos app on the iMac. Works fine everywhere else! Also, Messages doesn't work (sync), neither does Contacts. But that's another problem but probably related. Thanks in advance!
iMac 21.5″ 4K, macOS 11.2