First of all, I agree, never edit a csv file in Excel and then save it as a csv file. Excel is especially nasty with dates when this is done, but does not limit its nastiness to dates alone. I opened the csv file in Notepad and did a global search and replace to replace "12" with 12 and later back again so that I could experiment with the field being text and it being a number. With each iteration I flipped the fiscal period field on the Adagio GL import template back and forth between string and number.

Yes, we have recently upgraded Paymate, but that was several weeks ago. Since the Paymate upgrade we have had several successful weekly payroll exports from Paymate and imports into Adagio GL, all export and import parameters remaining unchanged. Adagio GL was upgraded last week and the import has not worked since then. This could be coincidence.

It is starting to look lke nobody else has seen this error message.