As I wrote in the other thread, my issues is below. Not the same error, but related I’m sure.
Installed 4.6.3 same error, rolled back, deactivated, and deleted. Reinstalled 4.6.3 and have the same issue. When I updated the plugin I then logged out of the dashboard and the screen goes blank, the usual WP login screen is not displayed, just a blank page.
If I go back to the forum page all displays as it should, but when I attempt to login from the forum page I get the same blank page and if I try to login from the wp-admin link, also a blank page.
on 4.6.2 I at least received the cookie error, now I just get blank pages when attempting to log in.