With such a wide variety of potential data which can be included in imports into Access Pay & Bill, sometimes they can fail for a number of reasons.
To help you identify why, we include an Import Error Log Enquiry screen which can be found in:
Click Timesheets and then select Data Import.
Select Import Error Log Enquiry.
By default, the date will be set to today, so please change this range as appropriate to pick up the affected attempted import's date.
Once the error described is resolved, you should be able to import the file again.