Most syncing issues can be resolved by fully exiting or "killing" the H2OPal app and then reopening it. You can do that by double tapping the iPhone home button and swiping the H2OPal app off the screen.
(on iPhone X models you need to swipe up, press and hold on the app and then press the close icon)
After a few seconds, you can then tap on the H2OPal icon to open the app again.
Please know that when syncing measurements H2OPal will normally connect to the iPhone app only for a second or two to transfer the data and then it will disconnect to conserve battery power. So for most of the time the bottle icon in the bottle of the home screen will NOT have a lightning bolt inside of it. if your smartphone is paired with and connects to many Bluetooth or Bluetooth Smart devices.
Potential issues may also occur if your smartphone is paired with and connects to many Bluetooth or Bluetooth Smart devices. In that case, other devices might be interfering when H2OPal tries to connect with your smartphone. If you believe this might be the case in your situation please let us know and we'll examine what would be the best solution in your case.
Also, having your iPhone in "Low Power Mode" may also limit H2OPal's ability to sync while the app is minimized (when your phone is locked, or if a different app is running in the foreground).
Your issue might be different, so if the above information doesn't solve it or if you have any further questions or feedback please create a support ticket or email us at firstname.lastname@example.org.