http://10.5.50.1/logout format should work, you can check this link> https://www.mikrotik.com/testdocs/ros/2.9/ip/hotspot.php
link_logout - link to logout page ("http://10.5.50.1/logout")
However you can customize that in the control center if its not working for you for some reason, just use custom and enter your own format.
What browser gives this error message?
