Unable to receive notification on HTC phone?

If your phone cannot receive notifications. Try the following steps and restart your phone:

Make sure that your phone is connected to network.

Check the settings of your phone.

Use HTC U11 (Android 8.0) as example：

1. Go to Settings -- Battery -- menu (top right corner) -- Battery optimization.

2. Battery optimization -- All apps -- Letstalk -- Don't optimize.

3. Go to Settings -- More (Wireless & networks) -- Data usage.

4. Data saver -- Unrestricted data access -- enable Letstalk.