Earlier quoted context omitted.
Here's what Microsoft won't tell you: If you buy standalone office and it is not allowed to phone home to Microsoft at least once a month, it stops working. This can happen if you use it on a disconnected computer or you just have a reverse firewall rule blocking microsoft domains.
I’m not sure that’s true. Last Office I bought was “Home Edition 2016” and it’s been running on a machine that doesn’t have internet access since 2017 without any issues.
If I block it from accessing Microsoft domains in Little Snitch, it goes into readonly mode after about a month. Opening a hole in the firewall lets it start working again. Previous versions from several years earlier didn't do that.