i suspected the htaccess too, zapped all of the Deny All, Deny from lines, and things started working again.
Started by disabling all add-ons, still failed. Thats when I changed the htaccess removing all of the Deny From entries and everything started working again. Thanks everyone for the fast response.
Looks like the problem is xf_session_activity is full issues. Getting pounded by robots even though I have the andyb htaccess edits to limit bots
Gobs of these:
You are getting that message because you have too many visitors looking at your site within an hours time. Take a look at Members | Current Visitors. You will probably see thousands of visitors and most of them will be Guests or Bots. Known bots can sometimes be a problem but if you look at the Guests IP Addresses you will see a lot of them are amazon servers. Those are most likely AI training themselves on your forums. If you are only seeing 3 or 4 thousand guests then what you can do is increase the table size that Xenforo uses for the xf_session_activity table.