I download to an external hard drive 346 GB then back again to my MacBook Pro 2015 model Montery. Then it came up with 'Unsupported library' update to latest version of photos..How can I get around this as its all my stored memory over so many years..
[Re-Titled by Moderator]
MacBook Pro 15″, macOS 12.7
Do you have two Macs with different system versions installed?
A Mac with macOS 12.7 Monterey cannot open a Photos Library that has been updated by a new version of Photos, for example the version of Photos installed by macOS 15 Sequoia.
If you want to share a Photos Library between Macs with different system versions installed, you may want to use iCloud Photos. iCloud can keep the libraries on devices with different system versions perfectly in sync and identical.
How can I resolve 'Unsupported library' error for photos on MacBook Pro 2015?
