Error: rpc error: code = Unauthenticated desc = InvalidSignature

I’ve built the example FUOTA deployment program, which returns “deployment created: ”

The Chirpstack FUOTA server prints:

INFO[24555] storage: deployment created id=8e318ae8-5395-491a-a65f-19243e3d704c
INFO[24555] storage: deployment device created deployment_id=8e318ae8-5395-491a-a65f-19243e3d704c dev_eui=68ef24cb64a1ad2e
DEBU[24555] fuota: stepCreateMulticastGroup funtion called deployment_id=8e318ae8-5395-491a-a65f-19243e3d704c
DEBU[24555] [transport]transport: returning. connection error: desc = “transport is closing”
INFO[24555] finished client unary call error=“rpc error: code = Unauthenticated desc = InvalidSignature” grpc.code=Unauthenticated grpc.method=Create grpc.service=api.MulticastGroupService grpc.time_ms=18.933 span.kind=client system=grpc
ERRO[24555] api: fuota deployment error deployment_id=8e318ae8-5395-491a-a65f-19243e3d704c error=“create multicast-group error: rpc error: code = Unauthenticated desc = InvalidSignature”

I can’t figure out which signature is being talked about. I’ve tried adding TLS credentials to Chirpstack FUOTA and enabling TLS, but then it tells me the server is using the “insecure” credentials (it was built as cloned from Github).