If the Sync window does not appear immediately, then refresh the screen by loading a different day in the diary then return to the current day.
A failed sync will report errors so you should open the call and attempt to resave it.
Pressing the (i) info button will open the call so you can check if your changes were recorded correctly.
Open the order by pressing the (i) info button to review it for any changes or apply any necessary deals before re-saving the call.
It is critical that you release the order after the call has synced, especially if you intend on having it sent, otherwise it will remain on hold until you do so - potentially forever.
The option to take the order off hold is in the Order Options of the order.