I changed my version of Excel from 2016 (school licence) to the 2013 version. 
Now when I try to export the data from PI Toolbox to Excel it always give the same fault: Fail: invalid path or filename.
I'm sure that the path and the filename are correct.
So I tried to creat an Excel with the Excel reports display and it says that PI Toolbox can't open Excel.

Can you help me?

Kind regards
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I had the exact same problem.  It drove me crazy for months.  The problem is that when you uninstall Excel 2016 (Office16) not all the registry keys are cleared.  Despite using several registry cleaners, I still had the problem.  Finally, I manually searched the registry (using "Registrar Registry Manager") for the string "Office16\Excel.exe" and then deleted those keys.  The problem was that these leftover registry keys pointed Toolbox to a version of Excel that was no longer installed on my computer.  After deleting the leftover keys, all went back to normal.

I hope this helps.
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