Models Builder: Run Custom Tool Suddenly Failing

We are running an Umbraco site in v8.18.8. We have not had the time to upgrade to the new versions. We have been using Models Builder for the past 3 years. I have been able to run the Custom Tool when I make updates. Over the past two days I have been hitting an error, which pops up immediately.

UmbracoModelsBuilder: Starting v8.0.5 7/31/2024 3:18:30 PM.
UmbracoModelsBuilder: UmbracoModelsBuilder failed to generate code: Exception: Response status code does not indicate success (NotFound)

UmbracoModelsBuilder:    at Umbraco.ModelsBuilder.Api.ApiClient.EnsureSuccess(HttpResponseMessage result)
   at Umbraco.ModelsBuilder.Api.ApiClient.ValidateClientVersion()
   at Umbraco.ModelsBuilder.CustomTool.CustomTool.UmbracoModelsBuilder.GenerateRaw(String wszInputFilePath, String wszDefaultNamespace, IntPtr[] rgbOutputFileContents, UInt32& pcbOutput, String& errMsg)

I’ve checked to make sure the solution builds and that the Umbraco credentials I have are correct and the instance they point to is up and running.

Is there any way to get more information about this error? I have a hard time imagining that it is to do with messed up document types because the error does return immediately.

Thanks for any help.

Angus


This is a companion discussion topic for the original entry at https://our.umbraco.com/forum/114487-models-builder-run-custom-tool-suddenly-failing