If I insert a new row and Paste (into A1, or highlight the entire row), that works. That’s what I do when I can’t simply insert a row. It would be much more convenient of I could just insert a row.
No, you can’t have multiple tabs in a .csv file.
The error is consistent in the files. That is, Company_A_File will always get the failure, and Company_Blort_File will always be successful.
No filters in the .csv file. (I don’t like filters, because I don’t know what they do. So I always turn them off in an .xls or .xlsx file.)
I just created a new spreadsheet and put some garbage in the first row. I created another spreadsheet with several rows of garbage in range A1:E6.
I go to the first spreadsheet, select the first row, copy. Then the second spreadsheet, select cell A1, Insert Copied Cells, and it inserted the entire row and my data in the second sheet is now in A2:E7.