What finally fixed it (the create new worksheet grayed out) for me was to follow Microsoft's Repair Office Installation - make sure that you close Quickbooks first and leave it closed while the Office Repair happens.  ALSO - make sure that you choose the Online Repair (not the Quick Repair) when doing the Microsoft Office Repair.  Once the Microsoft Office repair is done, THEN open Quickbooks, and the create new worksheet is finally not grayed out!!!   There is a link in this feed on how to do the Office Repair, but for mine in Windows 10, this is what I did:

1.  Right click the Windows Start button

2.  Choose Apps and Features

3.  Scroll down to Office 365 and click once.

4.  Click Modify - follow the prompts - this is where you need to make sure you choose Online Repair (not Quick Repair).   This took my computer a good 10 minutes. 

5.  Once the Office repair is completely done, then I opened up Quickbooks, and the Create New Worksheet option when exporting to Excel was finally available (not grayed out).