MyBB Community Forums

My forum:
www.langenort.nl/forum

My problem:
- Nobody can log-in. 

Quote:Authorization code mismatch. Are you accessing this function correctly? Please go back and try again.

- And it is not possible to make a new account (usernames don't turn green and all e-mail adresses are deemed invallid)

The admin page is accessible

MyBB version:
1.8.22

My technic admin already tried: 

<input name="my_post_key" type="hidden" value="{$mybb->post_code}" />
added in all templates with this Items:
error_nopermission
header_welcomeblock_guest
member_login
portal_welcome_guesttext

Done these setting:
$settings['cookiesecureflag'] = "0";
$settings['cookiedomain'] = ".langenort.nl";
$settings['cookiepath'] = "/public_html/forum/";
$settings['bburl'] = "http://langenort.nl/forum";

Default and recent updated templates tried

Please change Cookie Path (cookiepath) to /forum/ whereas your current setting is /public_html/forum/.

Read more on login issues and cookies setting: https://docs.mybb.com/1.8/faq/login-problems/ .

Thank you, it worked!