Remove invisible function.
 

Okay so i'm working on a site that's pretty old, just got hem upgraded to 3.8.7 from 3.7.3 and the set invisible option isn't available through usergroups, which is odd but anyway i removed the option from edit options however, a few users had set themselves invisible prior to the upgrade and such.

What is the query to undo this and have them un-invisible? I know there is one.....just not sure what it is? Thanks :)

UPDATE user SET options=options - 512 WHERE options & 512

Try this on your test site first.