Is the Library 2 syncing with iCloud Photos? You cannot import from a library that is syncing with iCloud. To import from your iCloud Photos Library, duplicate it. Then try to import from the copy of of the iCloud Photos Library. This will only work, however, if you are not using the "Optimize Mac Storage" option for iCloud Photos. All original image files need to have been downloaded from iCloud.
And your Mac needs to have been upgraded to macOS 12 Monterey or later. See: Import photos from another library in Photos on Mac – Apple Support (UK)
Older versions of Photos do not yet support the importing of photos directly from another library. You would have to export from one library, then import the exported items to the other library.