Some of our devs were running into this issue when using the emulator with specific versions of Windows. We found an answer while reviewing this documentation. For newer versions of the GRPC.Net.Client lib, there are some caveats about using the defaults on full .net framework.

We ended up specifying the GrpcCoreAdapter when using the emulator.

clientBuilder.GrpcAdapter = GrpcCoreAdapter.Instance;

That resolved the issue for us.