RichardHeart, as we discussed with Qyron below, the APK has been modified to print golang's standard library net package error message directly to the user.
If you get a moment, could you run the new APK and tell us what the net package is saying?
We expect something like "write to UDP6 ... network unreachable", but if would be informative if the error is something different.
On the first blank screen I try to input "soft1", then I see some sort of connection dialog but then I get error message which, again, is not visible. Attaching link to Dropbox folder with screenshots. https://www.dropbox.com/sh/tagc4veaeco8umm/AAA2xcvvLQoM_lUh1...
The error message (which you can't see) is probably telling you that your Internet connection is blocking Melondream's UDP packets. Are you connecting from work or public WiFi?
Btw, the lesson here for developers is: don't use UDP, use TCP. We made a big mistake
The system was built from the ground up to use forward error correction over UDP. The point was to allow a much less expensive, super-efficient server. We had no idea how poorly UDP is treated on the Internet. Huge, fatal mistake
Now interface works well. But still no connection. I've tried both cellular internet (where UDP is most probably blocked) and home WiFi which doesn't block UDP (for sure, I tried pinging from phone).
When the keyboard appears, it should be asking you to enter a server ID (and you should type in "soft1").