Sync Event issue when switching to new phone

Sync Event issue when switching to new phone

I recently got a new I phone 6.  I previously had an Iphone5.  When I signed into the app on the new phone, some of my events that I had did not sync with the new phone.  I went back on the old phone and they were still there, and they are on my desktop version (from the Zoho site).  Why would they not sync to  the phone, and how do I get them to sync.