Why Excel 2016 wont open XLS files in Windows. Please share different methods as well as workarounds to fix the issue.

Excel 2016 wont open XLS files due to compatibility issues, which is a common problem. It usually occurs after upgrading the MS Office or Windows OS. However, this problem may also occur even after a minor MS Office or Windows update.
Follow these methods in the given order of sequence to resolve €˜Excel 2016 wont open XLS files issue and open the XLS files in Excel 2016.
Open XLS File from MS Excel 2016
Instead of opening XLS file by double-click, open the MS Excel 2016 first and then,
Go to FileOpenBrowse
Navigate to the XLS file that wont open in Excel 2016
Select it and click €˜Open. This should open the XLS file without any issue

If you cant open the XLS in Excel 2016, then the XLS file is probably corrupt which can be repaired by using this Excel repair software from Stellar.