Office for the web does not work

Hi guys

I tried to configure office for the web, using Microsoft 365 and following this tutorial:

Setting Up the Office for the Web Backend Service for the New M-Files Web.pdf (Desktop, Web, Mobile)

Moreover, I configured/activated Office for the Web under advanced configuration - Client - Web.

However, I face the problem that the Office Online Editor does not open, showing exactly this issue stated in chapter 4.4 in the above tutorial. I did the changes on IIS, but still it does not work.

Anyone an idea where the error could be?

Kind regards,