This error generally appears in the following situations :
Scenario 1
There are hidden sheets in the XLS file. You must unhide the sheets and the sheet which contains data that you want to upload into Tally must be kept as the 1st sheet.
Scenario 2
While importing data from Excel into Tally, if you manually open any Excel sheet (the same file or any other excel file), in such situations you may get the aforesaid error.
Note:
You must not manually start Excel while udi-Magic is running. Although, you can open any Excel sheet(s) prior to starting udi-Magic and keep them opened, but should not manually move in Excel sheet or add/edit any data