WordPress login Not Acceptable

to start…
I have this error message when I try to login (don’t even need to fill anything and click log in, this message appears too)

 Not Acceptable

An appropriate representation of the requested resource /wp-login.php could not be found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request. 

but then the page title says 406 Not Acceptable

I have search around and saw some posts with .htaccess and I tried but still can’t get it to work.

Ok how this happened was, I was using Chrome and logged in for hours doing my stuffs. But then because of some reason I had to reset password for the original user named admin. So then after password was reset, I tried to login with firefox and the error appeared. At first I thought there’s something with admin user so, since my chrome is still logged in (my own login is roled as administrator) I used my login to delete the admin user and created a new one with other name.
Then I tried with firefox again with the new name I created I saw the error. Then I used my own login and same error happened. Then I realized, I don’t have to do anything and just by pressing login this error happens.

Now I am afraid to close my Chrome because it’s still logged in and working there.

P.S. I tired adding this too

<IfModule mod_security.c>
   # Turn off mod_security filtering.
   SecFilterEngine Off

   # The below probably isn't needed, but better safe than sorry.
   SecFilterScanPOST Off
</IfModule>

in .htaccess where is located same location as wp-config and others

P.S this is getting more confusing for me. I tried using my phone and co-worker’s phone to login into wp-admin and works like nothing ever happened. But I used both of our desktop to login into wp-admin and both desktop tried firefox and chrome. Same errors.