Currently all my label assignments
Just to be clear, you're saying that your labels are still there, but all the messages you manually added to them are no gone from those label views?
Or, are you saying the labels themselves are gone?
The former is a problem with the files in the index folder and or omailbase.dat. The only way to fix those is to restore them together from a very-recent backup (anything that happened after those old files will be like it didn't happen).
The latter is a problem with index.ini. Restoring it from a back should fix that (anything that happened after will be like it didn't happen).
You can check the database, to see if that helps, but it's unlikely that it'll help.
If all else fails, you'll have to fix things the hard way (save and open locally to read).