What is the level of inaccuracy (in terms of seconds/minutes) are you talking about?

From my past experience, I found that  time synchronization policy does not support all device brands/models and device-enrollment modes.  Have you performed any simple quick test (e.g. by manually setting a big time offset on the device and see if the device time get updated within the sync interval)   to preliminarily confirm that the policy works on your targeted device model.   If not, please do so first.   

If it works, but there is some intolerable offset all the time, then I suggest you to open an official support ticket with Soti support team to see if there can be any possible fix.