Google assistant manual linking error

There are quite a few articles and videos out there, all of which seem to suggest the same steps for integrating Google assistant with HA. Some of the better known content editors include JuanMTech and EverythingSmartHome.

I don’t think that the problem lies with the methodology and as far as I can tell, I have replicated the steps exactly. However, there is something within the way that I have setup my instance of HA that prevents the final linking within the Google Home app where I receive a message:

Has anyone had a similar issue or knows perhaps how to fix this?