authentication failure

We are upgrading our Citrix environment from XenApp 6.5 to XenDesktop 7 (still streaming apps). We use PC Extender with our old 6.5 environment and it works fine. But with 7, when a user logs on we get an "authentication failure" message.

On 6.5 we used citirx web interface and now we are using storefront. Any thoughts on what could be different?