My calendar will not sync with my iphone. The message says "Sync server failed to sync iphon"

(iPhone 6s) Running Fantastical calendar

My calendar will not sync with my iPhone. The message says "Sync server failed to sync iPhone"

I haven't had this problem before. I did a software update today. Went to sync on iTunes and all

is fine but at the end of sync this message pops up.

Tried several times

Tried iCloud and Computer sync

Tried WiFi and cable

Thanks