can't import images: unrecognizable file format
Images originally imported into Photos, png format exported & loaded to Flickr, and then downloaded from Flickr because the drive my album was on has gone south. I made a new album, imported 2 images just fine, and after that, all I get is the infamous "unrecognizable file format" error. The images are good; I can open in Preview and export as either png or jpg. These do not import, either. And I've run the library repair tool.
The library is in the Pictures folder. The images are on an ssd drive, but also fail when copied to Pictures.
MacBook Pro 13″, macOS 11.4