BigQuery - 'Edit Credentials' in Power BI Service no longer works

When publishing a dataset with BigQuery in Desktop and editing the credentials in the PBI Service, the data source credential is popping up a screen that shows basic auth rather than using the service account via OAuth. This does not work, and we can no longer authenticate to a BigQuery source in the service. Desktop is no issue.

This is Direct Query mode, FYI.

Anyone having this issue? It's broken the ability to publish datasets.