500 error when requesting mail API for messages

500 error when requesting mail API for messages

I'm following the search email documentation.

I made a request for 
http://mail.zoho.com/api/accounts/724572269/messages/search?searchKey=subject:meeting and I'm getting:
{ "status": { "code": 500, "description": "Internal Error" }, "data": {} } What could this be from?