Kendra Google Drive Connector fails with no details or logs

I am setting up a Google Drive connector. Normally when connectors have issues they output to Cloudwatch and state the reason for the failure under the Details column in the sync log. This connector is not logging anything and just displays a red alert at the top of the connector dashboard page which says:

We couldn't sync all files in the following data source: '[source name]', at start time [time]

It does this after almost exactly six minutes each time a sync is attempted. The Google Cloud Console doesn't show any logs or metrics for the Service Account credentials I'm using, so it seems like it's not attempting the connection.