Do you know if the user was logged into the correct account on your WordPress site before they logged into your forum? If so, then the problem may be due to your recent changes that you mention here: Revisioning community - customer flow?.
If knittingtoday.com is not the same WordPress site as was used for clubknit.knittingtoday.com, then you are going to have to login to the rails console of your Discourse site and run the command:
SingleSignOnRecord.destroy_all
Let me know if this doesn’t make sense, or if you have trouble getting it done.