I was trying to migrate my Apple Photos Library to Lightroom CC and got an error. I accidentally clicked the wrong button to end migration and now am stuck with a partially migrated library. What can I do to finish the migration? Lightroom won't let me migrate the library a second time.
There really isn't a user-facing way to restart an aborted migration. It is possible to do this via a script that we would provide.
Notes from the test engineer: "To avoid duplicates, the user would need to delete the assets that were partially migrated. They can find the assets in the recently added folder. We can provide a config.lua script which allows re-migration. They would need to restart Lightroom and run Apple Photos Migration again."
If this sounds like something you want to attempt, let me know and I will contact you off-forum to deliver a script.