Who Me Too'd this solution

Well, there's the obvious explanation that the username or password are incorrect.  But I'm assuming you posted because you know that not to be the case.  Troubleshooting this needs a lot more information, because it could be any number of things at this point.  As a next step, I'd look at the authentications logs on the firewall where you have the portal/gateway.  Under the Monitor tab, this is found under System.  I might further suggest you start with this filter and see if anything in the descriptions gives you a good lead:

(( subtype eq auth ) or ( subtype eq globalprotect ))