I have a similar problem. When I try to login to my site I see:
Fatal error: Class ‘WP_Session_Tokens’ not found in /hermes/bosoraweb123/b60/ipg.johnvandalencom/wp-includes/pluggable.php on line 884
I asked for a password reset using the username email address.
I got the reset email from WordPress with a link to follow to reset the password. When I went to the link, I saw “Sorry, that key does not appear to be valid.”
What do I try next?