Hi, Thank you for your feedback!

We've checked to find your account working well.
And we've tested Doit.im 5.4 for iPhone and not found the sync problem. Please tap 'Sync' in Settings to see if it works.
If not, could you please give a detailed explanation as for what you came across, like, "I added a task on web version, but it doesn't show on iPhone".

Have a nice day!