This is not a click-to-run web installer. Download the entire ISO or executable file once, then install on any supported PC without an active internet connection.
You installed using the offline source, but you are signed into a different Microsoft Account than the one tied to the key. Fix: Use the ospp.vbs script (located in C:\Program Files\Microsoft Office\Office16 ) to manually install the key via command line. office 2019 standard offline installer
Check for updates: Open Word → File → Account → Update Options → Update Now. The offline installer contains the base RTM version; you should connect temporarily to grab security patches. This is not a click-to-run web installer
Assume you have the official ISO or the generated folder on a USB stick. Fix: Use the ospp
An internal server that handles activation for your organization.