If you find that after inviting friends, your reward progress bar does not update and no new friends appear in your friend list, we suggest you confirm with your invited friends whether they have successfully downloaded and entered the game through the link you shared:

If not, please tell your friends to click the shared link to download the game again.

If it works, it's probably for one of the following reasons:

The invited player redownloaded the game due to network issues.
The invited player has network issues during the game loading process, resulting in disconnection and reconnection.
The invited player quits the game without successfully following the tutorial and enters a slot. Since this is a one-off mechanism in the game, you cannot invite the same friend to regain progress after the progress bar failed to update.

When you get any of the issues above, you can contact us at any time with information as follows:

Your game ID.
ID of your invited friend. 
Screenshot of your friends invite progress.