Export from librarything won't reimport

I exported 800 books from my library. I edited the tags. Then I tried to reimport them. I didn't change the CSV column order or the titles or any other information. I just updated the tags.

Now when I try to reimport it, it won't recognize 600+ books because they don't have ISBNs. Librarything didn't include the ISBN when I exported them. In fact, most of my books don't even have ISBNs. They have ASINs. The work ID hasn't changed but Librarything isn't referencing that.

What can I do?

Nothing so far as I know. It's something people have been begging to have for a decade or so. Closed import or something like that is what you can search for in talk. At some point I think Tim gave a rather technical explanation as to why it can't happen, so don't hold your breath.

Librarything will happily import 600+ of my books as new books. It won't match them to the books I have currently in my library. They have all the same data. I'm not sure why the matching won't work. Is this a bug?

Nope, it's just not a function. It never has been so far as I know and I've been here 19 years. There are others who could probably explain better, but it's been talked about for a long time.

Unfortunately, matching your records with existing records is just not something that can be done. You can add tags in LibraryThing (try using Batch Edit to make this go faster), or you can export a file, delete your library, add the tags to the file, and re-import, losing any data which is not available on the export file. These are your only options with the way LT imports/exports currently work.