Runtime Logging

Switch on the runtime logging to generate a log file.
link - docs.microsoft.com/en-us/office/dev/add-ins/testing/runtime-logging
You can use runtime logging to debug your add-in's manifest as well as several installation errors.
This feature can help you identify and fix issues with your manifest that are not detected by XSD schema validation, such as a mismatch between resource IDs.
Runtime logging is particularly useful for debugging add-ins that implement add-in commands and Excel custom functions.
Runtime Logging affects performance so turn it on only when you need to debug issues with your add-in manifest.

Runtime logging on Windows

Make sure that you are running Office 2016 desktop build 16.0.7019 or later.
To enable run-time logging

npx office-addin-dev-settings runtime-log --enable 

This will add the RuntimeLogging key under

HKEY_CURRENT_USER\SOFTWARE\Microsoft\Office\16.0\WEF\Developer\. 

Set the default value of the RuntimeLogging key to the full path of the file where you want the log to be written.

To enable runtime logging only for a specific file, use the same command with a filename:

npx office-addin-dev-settings runtime-log --enable [filename.txt] 

To disable runtime logging:

npx office-addin-dev-settings runtime-log --disable 

To display whether runtime logging is enabled:

npx office-addin-dev-settings runtime-log 

To display help within the command line for runtime logging:

npx office-addin-dev-settings runtime-log --help 

Runtime logging on Mac