NetGuard | A simple way to block access to the internet per app

I'm facing a problem with an http request done in HTTP.java.

On desktop all works fine (that request is not performed because it's necessary only on Android).

In Android all works without that http request.

After that that http request is made, all others fail after timeout with UnknownHostException error, as if they no longer have access to the internet connection, even if it is active. Also after minutes and after the onResume all http requests fail. Although the app cannot get an http response, the AdMob ad appears in my App, so I think that probably the connection works (or does the AdMob library cache some ads and show them when needed?).

Often, in these cases sometimes it works again:

• uninstalling and reinstalling the App from Android Studio
• closing the App, waiting some minutes and reopening it
• clearing App data from the device
• waiting an undefined amount of time

❗ After several attempts I discovered that as soon as the problem occurs, almost every time, if I activate the airplane mode and then disable it, the data connection is deactivated and then reactivated, and the App can immediately execute all subsequent http requests without having to do anything else on your device and without even having to reopen the application.

• tested with wifi on a 1GB fibra network: same error
• I checked the connection: it is stable, in wifi and also with SIM
• in the manifest there is the permission for using internet (otherwise it would never have worked)
• at the same time, the same App on desktop works perfectly and at the best speed, receiving http responses in less than 1 second, so the server isn't the problem
• I tested also with the url https://www.google.it: same error, the same url is reachable in the device via browser in less than 1 second
• as in the line .timeout(10000) I'm using a timeout of 10 seconds, the server has timeout set to 60 seconds
• checked the server SSL "quality" at https://www.ssllabs.com/ssltest: got "A" in "Overall Rating"
• done the SIM "reboot" directly with a Vodafone operator

I'm testing on a real device with a flat 4G connection and with wifi, with "NetGuard - no-root firewall" VPN App installed.

This VPN works very well with all the other apps and probably mine too, but I can't rule out that it's the problem, although I hardly think it is (I use it since years without problems).

There is something wrong in my code? Or at least, how can I know the exact cause of this error?

Thanks.

AndroidLauncher.java: