I was creating a brand new forum version 3.2.7, and once I tried to login to the admin account it failed, could not even use the 'forgot my password' because it said the email I had used was invalid (which it wasn't). Found this thread and realized I was using Chrome (Version 74.0.3729.169 (Official Build) (64-bit)) so I tried installing Firefox and logged in, worked fine.
When I was checking the version number of Chrome to add to this post, it started updating. So I will try the login again and update this post if this update fixes anything...
edit: nope, still broken login after Chrome update (Version 75.0.3770.100 (Official Build) (64-bit))
on Windows 10, if that matters.