not able to upgrade from a free account

I have set up whmcs provisioning to provision both free and pro accounts

creating and activating the account works just fine
however if a client is a fee member and clicks on one of the plugins only for upgraded members they get a message
this site has been permanently given status choose a different site

Is this a normal function or should the member be directed to a page allowing them to upgrade through the pro sites plugin installed on the site