Please use the option Settings > Create support email to send me your logfiles from both devices. I can then take a look what is happening with the sync.
For best practices on how to setup the sync, see here: https://stagetraxx.com/user-guide/cloud/#working-with-icloud-sync
I will create new thread next week here in the forum about more best practices as I now have identified some patterns of what works well and what does not work based on user feedback.