Login logout Cookie problems. Please watch the attached video

[hwmana]

Do what i said originally and disable this file temporarily - it's those cache contents that's causing a problem for MyBB.

Rename the .htaccess -> clear your browser cache -> restart the browser

Do that and report the result to us here.

Afterwards, when you confirm that this is the problem, you need to examine those cache rules one by one

PS: Is that the .htaccess that comes standard with Wordpress ?

Yes, that's the standard wordpresshtaccess file. I will do it and post the results here.