Cannot add apps - token failed office.com validation

Hi,

We've just setup our Sharepoint 2013 server for apps following this article: http://technet.microsoft.com/en-us/library/fp161236.aspx However get the "Everything is fine, but we had a small problem getting your license. Please go back to the SharePoint Store to get this app again and you won't be charged for it." error.  I am not using the farm account to add the apps as is a common issue for this error.  Looking in the logs I get the following:

The token failed Office.com validation. responseStatus:Malformed; eToken:<r v="1"><t aid="WA104092836" pid="{2b6fe79f-4c5c-45df-96f3-d253871d8cc3}" cid="5D3BEF9CA7512FB8" did="{9F2403EE-4E63-48DB-9F4C-A53A2A83DBD9}" ts="0" sl="true" et="Free" ad="2013-07-12T03:14:54Z" sd="2013-07-12" te="2014-07-12T03:14:54Z" ss="0" /><d>/84sfCGxLorG/Z03wYO2H96WA3+BKDWp0jR6YSxACII=</d></r>ca302e9c-fe57-b07c-c65c-0a2ecf4f2367

Any ideas?

Thanks