Please try the following steps if your iPhone app appears to be stuck on the initial green launch screen.
1. Force close the Tip Yourself app - https://support.apple.com/en-us/HT201330
2. Put your phone in Airplane Mode with wifi off. (Completely disconnect from the internet)
3. Open the Tip Yourself app - You should be taken to the login page
4. Turn off Airplane mode and enable wifi to reconnect to the internet
5. Login to Tip Yourself.
If you continue to have an issue logging in, please try completely deleting the Tip Yourself app from your phone and reinstalling from the App Store.
Please contact Support@tipyourself.com if you continue to have issues after reinstalling.