Fixing an Error that Occurs During Report Processing

How do I fix this error:

System.Web.Services.Protocols.SoapException: An error has occurred during report processing. ---> Microsoft.ReportingServices.ReportProcessing.ProcessingAbortedException: An error has occurred during report processing. ---> Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: Cannot create a connection to data source 'dsTechPROCompany'. ---> System.Exception: For more information about this error navigate to the report server on the local server machine, or enable remote errors at OmniByte.TechPRO.WebAPI.Utilities.EmailSender.SendCheckoutEmail(String ServiceCallID, String Appointment, String Technician, Boolean EmailToTech, String reporttype, Int32 checkoutLogID, List`1 customerattachments, List`1 technicianattachments, Int32 QueueID, String DeviceID, Setting adminSetting) in C:\BuildPool\_work\1\s\WebAPI\OmniByte.TechPRO.WebAPI\OmniByte.TechPRO.WebAPI\Utilities\EmailSender.cs:line 328 at OmniByte.TechPRO.WebAPI.Controllers.ERPFullAppointmentCheckoutController.Get(Int32 checkoutLogID) in C:\BuildPool\_work\1\s\WebAPI\OmniByte.TechPRO.WebAPI\OmniByte.TechPRO.WebAPI\Controllers\ERPFullAppointmentCheckoutController.cs:line 354

The SSRS server was unable to connect to the database. Reprocess the checkout