have you used the same domain admin account used to run the task to update the register at least once through the sage 100 desktop?

At one point, I recall various forms/reports had to be printed/previewed by a user at least once before it could be automated by a BOI script.

Thanks for the suggestion David, but same result .    In addition, the last couple of times it failed, it failed with 'The status of one or more batches has changed. Verify the current status and try again.'  Upon checking/verifying the batches, there were not changes.   In the end, the problem seems to reside somewhere in the context of running the application via scheduled task, as running the program manually ends in success every time.

Below is some code from one of my journal update scripts that goes through paperless office.  Try comparing methods I used to methods you are using.

RetVal = 0 : SY_Session.sLastErrorMsg = "" : RetVal = SY_Session.nSetProgram(SY_Session.nLookupTask("BM_ProductionRegister_UI"))
If RetVal <> 0 Then
	Set BM_ProductionRegister_Upd = SY_Session.oNewObject("BM_ProductionRegister_Upd")
	RetVal = 1
	If BM_ProductionRegister_Upd.nBatchEnabled <> 0 Then 
		RetVal = 0 : BM_ProductionRegister_Upd.sLastErrorMsg = "" : RetVal = BM_ProductionRegister_Upd.nSelectBatch(DestinationBatchNo)
		If ArgDebugPrint Then oScript.DebugPrint "nSelectBatch: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
	End If
	BM_ProductionRegister_Upd.nPDFSilent = 1
	BM_ProductionRegister_Upd.nSetPostingDate ModuleDate
	RetVal = 0 : BM_ProductionRegister_Upd.sLastErrorMsg = "" : RetVal = BM_ProductionRegister_Upd.nProcessReport("PRINT")
	If ArgDebugPrint Then oScript.DebugPrint "nProcessReport: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
	If RetVal = 1 Then
		RetVal = 0 : RetVal = BM_ProductionRegister_Upd.nEndOfPDFConverterJob()
		RetVal = 0 : RetVal = BM_ProductionRegister_Upd.nUpdate()
		If ArgDebugPrint Then oScript.DebugPrint "nUpdate: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
		If RetVal <> 0 Then UpdateDailyTransactionRegister = True
	End If
End If

Below is some code from one of my journal update scripts that goes through paperless office.  Try comparing methods I used to methods you are using.

RetVal = 0 : SY_Session.sLastErrorMsg = "" : RetVal = SY_Session.nSetProgram(SY_Session.nLookupTask("BM_ProductionRegister_UI"))
If RetVal <> 0 Then
	Set BM_ProductionRegister_Upd = SY_Session.oNewObject("BM_ProductionRegister_Upd")
	RetVal = 1
	If BM_ProductionRegister_Upd.nBatchEnabled <> 0 Then 
		RetVal = 0 : BM_ProductionRegister_Upd.sLastErrorMsg = "" : RetVal = BM_ProductionRegister_Upd.nSelectBatch(DestinationBatchNo)
		If ArgDebugPrint Then oScript.DebugPrint "nSelectBatch: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
	End If
	BM_ProductionRegister_Upd.nPDFSilent = 1
	BM_ProductionRegister_Upd.nSetPostingDate ModuleDate
	RetVal = 0 : BM_ProductionRegister_Upd.sLastErrorMsg = "" : RetVal = BM_ProductionRegister_Upd.nProcessReport("PRINT")
	If ArgDebugPrint Then oScript.DebugPrint "nProcessReport: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
	If RetVal = 1 Then
		RetVal = 0 : RetVal = BM_ProductionRegister_Upd.nEndOfPDFConverterJob()
		RetVal = 0 : RetVal = BM_ProductionRegister_Upd.nUpdate()
		If ArgDebugPrint Then oScript.DebugPrint "nUpdate: " & RetVal & " | " & "LastErrorMsg: " & BM_ProductionRegister_Upd.sLastErrorMsg
		If RetVal <> 0 Then UpdateDailyTransactionRegister = True
	End If
End If

Thanks David.  There are definitely some extra methods being called/properties being set in your example that I don't have in place.  It's a little concerning to me that the program will work fine when run manually and that I have the same program working successfully at another client via scheduled task, but whatever works!.  Will let you know how I make out.

Paperless office plays a part in this.  I recall at one point, you had to modify the pvx.ini file to contain the [Paperless] section from another file in order for paperless office to work with external BOI scripts.  Can't recall off the top of my head if that is still required on 2019+.

If you were calling ProcessReport with "EXPORT" instead of "PRINT" then you would handle the file path and format yourself but it would bypass paperless office so whenever possible if paperless office is configured, I want to leverage it.

There are a lot of things that comes into play with Windows Task Scheduler too, such as the account used to run it, whether you have the option checked to run whether or not the user is logged in, NTFS permissions of the Sage 100 MAS90 directory, Advanced vs Standard, etc.