In the most recent updates for Jelly SMS on iOS and Mac, I have removed the iCloud feature. The main benefit of this feature was to have all your messages and user profiles in sync between iOS and Mac OS X. However, iCloud is a complete and utter mess to deal with when using a Core Data database (which is the one recommended by Apple).
In early 2013, after years of struggling with Apple’s opaque and buggy implementation of iCloud Core Data sync, the issues reached a breaking point when developers called out the service’s shortcomings, culminating in a pointed article by Ellis Hamburger at The Verge.
I have tried several things, and no amount of testing can make sync’ing working reliably, as there are fundamental issues with iCloud on the platform level. This was causing problems for users such as profiles disappearing, and messages getting out of sync.
I may revisit it again in future if I get time, but for now, it is causing too many issues for users, and I have to pull the feature out altogether.