Reset Password Failing

I'm are updating a project from ci2 to ci3 and are having an issue with the reset password - I had thought it was a fairly simple fix to update the url in the password email - which does take you to the correct page however the password won't actually reset. First I was receiving the error message:

An Error Was Encountered

This form post did not pass our security checks.

I followed the advice on stackoverflow

Now I am not receiving an error message but when I test the login with the updated password it fails.

I am also having an issue where if you select log out it does not actually log the person out.

The only warning there is in the logs is Severity: Warning --> ini_set(): A session is active. You cannot change the session module's ini settings at this time
Does anybody have any ideas?
Many Thanks