Hi SWilyums,
I put together a very quick example to test a similar filter to see if I was able to figure out what could be going on but it seems to be working ok in my case.
Here's the code I've tried:
Dim dt As Datatable = BRApi.Import.Data.FdxExecuteDataUnit(si, "PeoplePln", "E#UK", "Local", scenarioTypeId.Budget, "S#BudgetDefault", "T#2021M5", "YTD", True, "UD1 = 'None' And (Account = 'Bonus' OR Account = 'Staff Costs' OR Account = 'None')", 1, False)
Stupid question I know 🙂 but have you double checked that there's data for that exact combination you are filtering? 
I've ran my test on v8.2.0 and I don't see anything wrong with your filter so the only options that come to my mind are version related or that the combination of filters does actually result in no data.
You can use the following function to print the content of your data table, maybe that can help you with the debug:
Public Function PrintDataTable(ByVal si As SessionInfo, ByVal dt As DataTable, ByVal Optional strSeparator As String = "|", ByVal Optional limit As Integer = 0, ByVal Optional boolPrintTableName As Boolean = True, ByVal Optional list As List(Of String) = Nothing, ByVal Optional strTextSep As String = Nothing) As String
	        Dim strLog As New text.StringBuilder
			Dim strBRName As String = System.Reflection.MethodInfo.GetCurrentMethod().Name
			Dim listColToSkip As New List(Of String) ({"None"})
		    If Not IsNothing(list) Then
		        listColToSkip = list
		    End If
			strLog.AppendLine(String.Format("{0} - Sep: {1}, Limit: {2}, Print Table Name: {3}, Col(s) To Skip: {4}", strBRName, strSeparator, limit.ToString, boolPrintTableName.ToString, String.Join(", ", listColToSkip)))
			
			If strSeparator.XFEqualsIgnoreCase("tab") Then
				strSeparator = vbTab
			End If
			
			Try
	            Dim result As New Text.StringBuilder
				
				If boolPrintTableName Then 
					result.AppendLine("Table name: " & dt.TableName)
				End If
	            Dim header As String = Nothing
	            For Each dc As DataColumn In dt.Columns
					strLog.AppendLine(String.Format("{0} - Col Name: {1}, To Skip: {2}", strBRName, dc.ColumnName, listColToSkip.Contains(dc.ColumnName)))
					If Not listColToSkip.Contains(dc.ColumnName) Then 
	                	header = header & dc.ColumnName & strSeparator
					End If
	            Next
				If Not String.IsNullOrEmpty(header) Then
	            	result.AppendLine(header)
				End If
				If limit = 0 Then limit = dt.Rows.Count -1
				If limit > dt.Rows.Count -1 Then limit = dt.Rows.Count -1
	            For curRow As Integer = 0 To limit
	                Dim row As String = String.Empty
	                For curCol As Integer = 0 To dt.Columns.Count -1
						If Not listColToSkip.Contains(dt.Columns(curCol).ColumnName) Then
	                    	If strTextSep Is Nothing Then 
	                    		row = row & dt.Rows(curRow)(curCol).ToString.Trim & strSeparator
							Else
								row = row & strTextSep & dt.Rows(curRow)(curCol).ToString.Trim & strTextSep & strSeparator
							End If
						End If
	                Next
					If Not String.IsNullOrEmpty(row) Then
	                	result.AppendLine(row)
					End If
	            Next
	            Return result.ToString
	            
	        Catch ex As Exception
				BRApi.ErrorLog.LogMessage(si, strLog.ToString)
	            Throw ErrorHandler.LogWrite(si, New XFException(si, ex))
	        End Try
	        
	    End Function