Oh man, that sounds incredibly frustrating... I've seen this happen a few times when switching account types, and it usually boils down to the PC getting confused between your old personal Microsoft account and the new business one.
The good news is, a clean reset should definitely get you back on track. Here's how to break out of that loop:
When you're on the "Get Office" screen, press Shift + F10 on your keyboard. This should open a Command Prompt window. In that black window, type systemreset and hit Enter.
This will launch the Windows reset utility. Choose the option to "Remove everything" and then select "Cloud download" when it asks. This will grab a fresh copy of Windows from Microsoft's servers, which is the cleanest way to go.
After the reset, when you get to the setup screen again, be sure to sign in with your new business account email and password right from the start. That should bypass the whole "Get Office" prompt entirely.
This process will wipe all your data, so if you had anything important on there previously, you might need to recover it from backup afterward.
=====
Hope this gets you sorted! If it works, could you mark this as the accepted answer? It helps others find the solution faster too 🙂