Jaspersoft Server can't Run report with Webservice DS

Greetings,

I'm trying to run a report through jaspersoft server,

I've uploaded Report template and attached a Webservice Data source with proper URI (request Verb: GET)

But when I RUN report it pop's up Following error,

Error Message

There was an error on the server. Try again or contact site administrators. 

Can you please advice - what can be problem with server?

I've tried to use same Webservice DS on Jaspersoft studio and it returned success in result. But on server it popped up Error.