This might help:

https://support.na.sage.com/selfservice/viewdocument.do?noCount=true&externalId=115168

This might be helpful too:

Confirm the version of Excel and compare to the Integrated Solutions Compatibility Matrix (Knowledgebase article # 48274): 

Microsoft Office
2019 - 32 and 64-bit versions supported. 
2016 - 32 and 64-bit versions supported. 
2013 - 32 and 64-bit versions supported. 
2010** - **Office 2010 support by Microsoft ended on October 13th,2020 and is no longer supported by Sage.

See KB 53091 for more information.

Plus: 

Sage 100 Office Merge:

Desktop Versions only of Office 365, 2019, 2016, 2013. 

**Office 2010 support by Microsoft ended on October 13th, 2020 and is no longer supported by Sage.

Sage 100 Office Merge does not integrate with the Online Web Versions of the Office application.

The Excel button is only greyed out in Explorer.  If they do an F2 Lookup, the Excel button is there and they can export.

A little late to this party, but I found a solution to this for a few machines that ran into it after Office install/updates. The export selections were greyed out in Explorer for Excel and Word due to missing registry entries indicating install path of those two applications. To resolve, I added String-type entries to the below registry keys with the path pointing to the current installation directory for Microsoft Office. The path to Office will depend on version and 32bit VS 64bit installation. The linked help article was updated to reflect this fix but doesn't indicate the names of the registry entries needed for each key.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\excel.exe

• Add string entry "(default)" with value "C:\Program Files\Microsoft Office\Root\Office16\EXCEL.EXE"
• Add string entry "Path" with value C:\Program Files\Microsoft Office\Root\Office16\

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\WinWord.exe

• Add string entry "(default)" with value "C:\Program Files\Microsoft Office\Root\Office16\WINWORD.EXE"
• Add string entry "Path" with value C:\Program Files\Microsoft Office\Root\Office16\