Since I updated 2 of my blog to the 2.9.1 I've had the weirdest problem.
The categories and tags are gone. All posts are now under "Uncategorized" and I can't see any tags or categories on the admin panel.
I checked the database all everything seems ok there, the categories and tags are there.
I asked my hosting to: -reset the mysql, check the conections, fix the database, everything, but the problem remains.
Now the weird part, I thought the problem was the update, but now I see that all my blogs (even those that are not updated to the last version) are having the same problem.