The Import Error Logs are able to be seen in Access Pay & Bill and give the reason why something hasn't been imported.
Web Holding Area(WHA)
If you import into the WHA, you can find this in the Web Menu. At the bottom you have the Web Transfer Errors Enquiry and the Web Transfer Errors Report.
P&B:
If you import directly into Access Pay & Bill, to find the error logs:
Click Timesheets Menu and then Data Import.
Select Import Error Log Enquiry.