I have seen a lot of posts and information about SSL errors and I have stumbled upon one myself.
I am trying to access a web page through Android WebView with a GlobalSi
If you have a WebClient which overrides the onReceivedSSLError() function and calls the handler.proceed() API, it can solve the certificate issue of error 3, I tested on Android 4.4 and 6.0.
If you still get an errorCode(-1) in the function onReceivedError(), you need to check the server side implementation sometime, especially when you call the POST method instead of the GET method, because the server may return nothing if there is unexpected POST parameters.
Good luck.