When I attempt to build my models, I get a 404 error in the output window. It's 404 on this url: http://localhost:#####/Umbraco/BackOffice/ModelsBuilder/ModelsBuilderApi/ValidateClientVersion

Right now I have 2 doctypes, a BasePage with 3 properties and a Home that inherits BasePage as a composition.

I've got it set in my web.config:

<add key="Umbraco.ModelsBuilder.Enable" value="true" />
<add key="Umbraco.ModelsBuilder.ModelsMode" value="Nothing" />

And I have ModelsBuilder 8.1.6 installed running Umbraco 8.17.1

Edit: I uninstalled and re-installed Umbraco.ModelsBuilder and still the same error.

UmbracoModelsBuilder:    at Umbraco.ModelsBuilder.Api.ApiClient.EnsureSuccess(HttpResponseMessage result)
   at Umbraco.ModelsBuilder.Api.ApiClient.ValidateClientVersion()
   at ZpqrtBnk.ModelsBuilder.Extension.Generator.TryGenerate(ProjectItem sourceItem)
   at ZpqrtBnk.ModelsBuilder.Extension.Generator.Generate(AsyncPackage package, ProjectItem sourceItem)
UmbracoModelsBuilder: Starting v8.1.5 1/18/2022 5:01:04 PM.
UmbracoModelsBuilder: UmbracoModelsBuilder failed to generate code: Exception: Response status code does not indicate success (NotFound)

Interesting that it says starting 8.1.5 and I have 8.1.6 installed.

What am I missing here?