Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Check your Office settings and make sure that the Options > General > Privacy Settings.. screen has the "All connected experiences" option enabled so that you can then enable the "Experiences that download online content" option. (These are the steps for my Office 2016 Professional Plus running on Windows 10.) This should allow you to access the online Help system.