Excel fail to open the protected workbook

After running few days on client system, file is not opining and given error as below
Even new exe file provided same error is popup.

Regarding the issue you’re facing with the protected workbook, I recommend utilizing the “Decrypt Save” feature within XLS Padlock. Ask the customer to send you the XLSC save file, decrypt this file back to its normal workbook state and open it into Excel. After that, you can employ the Document Inspector tool within Excel to identify and address any errors that Excel reports.