Sync only works manually...
 

I've bought omnifocus on both iPhone and ipad. I have to manually sync for syncing to work. I'm using the omnisync server.

Any way to make it happen automatically?

-Verxion

You might be laboring under a misconception here. OmniFocus syncs at launch, 1 minute after you make a change, and hourly thereafter. It doesn't sync directly with other copies of OmniFocus, only with the central repository. Therefore, if you make a change on your iPad at t = 0, it syncs the change to the repository at t = 1 minute. The iPhone isn't going to pick up that change until the next time it syncs, contributing any local changes to the repository and collecting any which have been added by other clients, which (assuming it is always on, running OmniFocus, and connected to the internet) could be nearly an hour later, depending on the phase of its sync cycle. If you want to see that change on the iPhone immediately, and OmniFocus is already running, you might have to tap the sync button on the iPhone (and first on the iPad, if it hasn't been 1 minute since you made the last change there). Normally, no action is required, though it is a good practice to make sure that you sync after you make changes and when switching to another device.