.XLS file won't convert properly to .XLSX

I have a heavily formatted worksheet created in Excel 2003 under an older Windows (Win 98?). Now that I have Excel 2016 and Win10, I want to convert it to XLSX and pin it to the Excel jumplist. But no matter what I do, it comes up as something like "X10000014.XLS (Read-Only) [Compatibility mode]"

I have tried loading the XLS file and using file convert. I have also tried creating a new blank worksheet in Excel 2016, saving that, then cutting and pasting the data from the XLS file into it. Neither works.

How do I get this to work?

I should add that whenever I click on one of these "converted" files to open it, I first get a message "There was a problem sending the command to the program"

I should add that whenever I click on one of these "converted" files to open it, I first get a message "There was a problem sending the command to the program"

"Save as xlsx" doesn't do it. "Convert" means clicking File / Info / Convert.

1) In Excel 2016, when I open an XLS, click File, and hen Info, I get, among other things, a square with an Excel icon and the word "convert," just to the left of the note about Compatibility Mode. I'm not sure how to post an attachment, or I'd send a screen shot.

2) When I try File Save As, the file gets the XLSX extension but still opens in compatibility mode.

3) The file is 56 KB -- is that OK? How do I upload it? And I'll have to delete two columns of confidential info from that file.

Screenshot with convert button attached (I hope)

Here's the redacted file

Has anyone tried my file in Excel 2016?

Opens fine for me in 2016

I'm loading it from a local folder. Other files in that folder converted just fine.

If it opens in someone else's Excel 2016, there must be a problem with my system--but only with this file. Any suggestions?

Checking the revised file, I get the same results -- first "there was a problem sending the result to the program" then, after some seconds, it opens up in compatibility mode with a number as its filename.