A couple of things to try:

Use the script hosted in github, not the earlier one in this thread on google drive.

The script requires GPS location as NMEA is a relative format using bearing and distance for targets, instead of using lat/lon directly. It may be that you need to set the device outside for a bit.

Verify SkyEcho is sending UDP data to the android's IP containing traffic, you can view the raw UDP stream using an android app called UDP Monitor. Connect to the SkyEcho wifi, configure it to listed to port 4000 and you should see hex data streaming in. Traffic objects start with "7e14". There should be many of them. If you use UDP monitor you may have to restart the android phone before switching to the script.

The script only passes aircraft within 60km but it's unlikely you have no aircraft within that range.