MyBB Community Forums

After installing a fresh mybb script and adding an old database from 1.6, I've had some minor issues.  I've been able to fix most by getting rid of old plugins.  One thing I can't fix is the loading time is sluggish (the host is fine), but more important the login/logout.  I was able to login, but when I click logout.. it says
"You have successfully been logged out.
You will now be taken back to the forum index"

Then it redirects me to the board index, but I'm still logged in.  

Any thoughts?

And another user can't login.  They click login but nothing happens.

Perhaps the following information is useful for you:
https://community.mybb.com/thread-42123.html

Other thing that pops into my mind is that your theme might not be fully compatible with the new version you installed. Remember that 1.8 introduced jQuery as its JavaScript library and dropped... Prototype? I think that was it.

Either try to find an updated version of your theme, update it somehow, or switch themes.