From my router I can ping with no problems (I am in the United States):
My Sonoff switch is 192.168.21.110 of which I can ping with no problems. It has a strong WiFi signal.
If I open the app I can see my switch and control it without problems.
I regularly have problems with this device being reachable from the Internet/Google Home. What can I do to resolve these problems? I placed the switch in a ceiling fan in a very high up ceiling so I do not easily have physical access.