If I temporarily remove all access of a user to my libraries, the new Plex Web is permanently removing that user from my friend’s list. In order to give permissions to that user again, I have to type their e-mail all over and go through the wizard.
They made it complicated to access the new Friends list (https://app.plex.tv/desktop/#!/profile), but once there, you’ll see those users without library access. Once you click on one, you can then access “Manage Library Access” via the three dots up top.
Ok, to whoever is having the same problem as me, here’s how to give access to someone who you previously removed from your library:
go to one of the pages VBB or Dane22 mentioned and once you click on the user you want to give access to your library, they won 't have a Library Access button and you’ll have to click on those three dots in order to go to the page where you can finally choose the libraries you want them to have access to