If your contact is using an Android device, please have them check the following:
- Make sure they are running the latest version of Tango.
- Check to see that they don't have any background data or restrictions enable on their device
- Have them force close any other apps running in the background, while making sure Tango is running in the background
- Ensure your contact is connected to a strong network connection. If they are connected to their mobile carrier's network, have them connect their device to an available Wi-Fi connection
If your contact is using an Apple device, have them check their notification settings here.