When attempting to import transactions into AvaTax Admin Console, I receive "Unable to import the file. Must specify valid information for parsing in the string."
When using the transaction import template, make sure there are no additional columns after "BY" IsSellerImporterOfRecord. Any additional columns after Column BY should be deleted. It's possible the last column is entitled "Errors". The 'Errors column must be deleted.
Once deleted re-import the file into the Admin Console.