photos can't open from HD

[captainkarlos]

Hi there
Can anyone help me, I have a external hard drive with photos library on it, the version of photos it was saved on is very old. I recently opened the photos on a newer Mac and now I cannot open the HD on the older Mac?
The Mac is so old i cannot update the photo software. How can i fix the HD so i can access the photo library again on the older Mac?
Many thanks

 

[RhetTbull]

Once you open a Photos library on a newer version of macOS, the library is updated to the newer version of Photos. Photos changes the schema of the library with each release of macOS and once this is done, you cannot go back unless you have a backup of the library before it was migrated.