VPN Connection - Android Not Working , working fine IPhone
To see complete Android OS logs, you can easily use the logcat command in an ADB(Android Debug Bridge) console. There are two ways to do this: you can use the real adb by connecting your phone to a computer with valid adb drivers, or you can do it right on your phone by downloading a Terminal Emulator and running the logcat command there. The live logcat will spit out a lot of data consistently, so you'll want to filter it. Use logcat | grep (some keyword) to filter to only lines containing the keyword.

As for your VPN problem, Android's built-in VPN service, from my experience, is pretty faulty. You might want to install an external VPN client off the Play Store, such as OpenVPN Connect.

Hope this solves your mystery.