Can't create Linux Premium app in West US 2

When I try to create a new Linux Azure Functions app using the Premium EP1 plan in West US 2, I get the error:

> "Requested features are not supported in region. Please try another region."

I've done this before without error. This time is no different, but fails now for some reason.

West US 2 is on the list, so this should work - yes?
https://azure.microsoft.com/en-us/updates/functions-premium-region/

I read this: https://github.com/Azure/Azure-Functions/wiki/Creating-Function-Apps-in-an-existing-Resource-Group
But this fails even when creating a new resource group, app plan, app, etc.

Nothing complex about the setup.
Tracking ID from the portal: 15519ee7-5ebd-4f06-a1ad-88b3b0b28f1b

In case it matters, runtime stack is .NET Core 3.1, and I'm publishing code, not a docker container.

Start by reproducing the Linux Azure Functions Premium EP1 creation in West US 2 from the Azure portal, using a new resource group, app plan, and app. Review the linked Premium region update and existing-resource-group wiki guidance, and use tracking ID 15519ee7-5ebd-4f06-a1ad-88b3b0b28f1b when investigating the regional feature error. Done means the supported configuration can be created or the unsupported combination is clearly identified.

Written by the indexing model from the issue text.