Sorry, this was already logged but closed in error after getting an answer on enabling the Crystal Web Service Logs.
I have the same crystal report in 2 IFS instances. One works without any issues where as the second on fails with the No PDF report returned from Crystal Web Service.
On checking the log file I get the following:
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RGetSavedPDFReport] File Name : TnmtShpordBarc.rpt
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RGetSavedPDFReport] ParameterValues : 281.0 ,LangCode = gb
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-Rbase64Encode] for 281
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-Rbase64Encode] Encoded value : Mjgx
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-Rbase64Decode] for Mjgx
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-Rbase64Decode] Decoded to 281
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-ROpenReport] File Name : gb\TnmtShpordBarc.rpt
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RGetAppSetting] Get the value for OpenReportPath from Web.config.
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-ROpenReport] The file F:\IFS\IFSCrystal\IFSR\gb\TnmtShpordBarc.rpt is found
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RGetAppSetting] Get the value for OpenReportPath from Web.config.
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RLoadInfoServiceReport] Loading infoServe report : F:\IFS\IFSCrystal\IFSR\gb\TnmtShpordBarc.rpt
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RLoadInfoServiceReport] DBUser = IFSPRINT ,DBPassword : ******* ,DBServerName : IFSRPDB ,AppOwner : IFSAPP
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RLoadInfoServiceReport] Setting up logon information for each database object.
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RSetTableLocation] Set appropriate post-fixes for INVENTORY_PART_A
6/2/2020 10:04:06 AM IFSCRWebSetup_IFSR]-RSetDatabaseLocation] Generating fully qualified database object name for INVENTORY_PART_A
6/2/2020 10:04:07 AM IFSCRWebSetup_IFSR]-ERROR in iLoadInfoServiceReport] Error in loading infoServices report.
6/2/2020 10:04:07 AM IFSCRWebSetup_IFSR]-The table 'INVENTORY_PART_A' could not be found. Error in File TnmtShpordBarc 28736_26664_.rpt:
The table could not be found. at CrystalDecisions.ReportAppServer.Controllers.DatabaseControllerClass.SetTableLocation(ISCRTable CurTable, ISCRTable NewTable)
at CrystalDecisions.CrystalReports.Engine.Table.set_Location(String value)
at Ifs_ReportService.SetDatabaseLocation(String databaseLocation, Table table) in c:\inetpub\wwwroot\IFSCRWebSetup_IFSR\App_Code\Service.cs:line 1409
at Ifs_ReportService.SetTableLocation(Table crTable, String UserId, String AppOwner, String IALOwner) in c:\inetpub\wwwroot\IFSCRWebSetup_IFSR\App_Code\Service.cs:line 1381
at Ifs_ReportService.LoadInfoServiceReport(String path, String DBUser, String DBPassword, String DBServerName, String AppOwner) in c:\inetpub\wwwroot\IFSCRWebSetup_IFSR\App_Code\Service.cs:line 1204
All other Crystal Reports work in both environments.