Smart Device Management - Oauth consent option just bounces

[Jebber]

I've been following the guide for Home Assistant's nest integration, but it just tells me it can't link as soon as it redirects to GCP for permission.

Infuriatingly, when I'm in APIs and Services / Smart Device Management where it has the link to check the config for OAuth Consent Screen just bounces to authentication overview every time I click it, or even try to navigate to it another way. So perhaps that's related? It kind of pauses for a few seconds like it's trying to do something, and falling back to the overview screen.

The link I'm clicking (highlighted in grey):

Where I end up, not what I clicked on

I have tried everything I can think of (I use GCP in my day job, so I'm not inexperienced). I have even created a fresh new project, and set everything up from scratch again (following guides line by line), but it happens even with a new everything.

Is this a bug? Something on my account maybe? It certainly doesn't look like it's a "me thing", but if I can't get Google to fix it without buying support, what can I do?