Print Crystal Report From Server

hello there
i have server have crystal report form and i have web service and i have application that installed on PDT device so when i type number on PDT device the web service call the crystal report from server and filling the data requierd then send it to printer , every thing is ok exept the printing , when i need to print there is error message show in the PDT device .
error message :
System.Web.Services.Protocols.SoapException: System.Web.Services.Protocols.SoapException: Server was unable to process request. --->
so please some help