danielmai commented :
INFO: Java 9 ALPN API unavailable (this may be normal)
java.lang.ClassNotFoundException: io.netty.internal.tcnative.SSL
java.lang.ClassNotFoundException: org.conscrypt.Conscrypt
java.lang.ClassNotFoundException: org/eclipse/jetty/alpn/ALPN
Could not find TLS ALPN provider; no working netty-tcnative, Conscrypt, or Jetty NPN/ALPN available
What platform and Java version are you using? Is this with the latest JDK (Java 14)? Looks like your setup doesn’t have any of the ALPN providers. You need at least one to handle the TLS connections with gRPC. See gprc-java’s SECURITY.md page for more info on the TLS setup.