I am working on this bug in the Google Ads client library for Java. I have narrowed the cause to the fact that UnaryCallable.call(request) never returns when instantiated with RequestT of SearchGoogleAdsRequest and ResponseT of GoogleAdsServiceClient.SearchedPageResponse IF the access token cannot be created (e.g. if the refresh token is incorrect).

To reproduce, try running this example with an invalid refresh token.

The issue does not exist with other types of RequestT and ResponseT even with an invalid refresh token (e.g. UnaryCallable<MutateCampaignsRequest, MutateCampaignsResponse>).

This issue may actually stem from the OAuth library used in this library. However, I've tried tracing the issue, and my lack of knowledge regarding this codebase makes it challenging to actually see what's going on once the call method is invoked.