So this is a Sync 3 upgrade replacing Sync 2? Do you know the model (part number) of the APIM?
What version of Sync 3 is loaded in the unit?
This can caused by a failing APIM, or an APIM that has no memory for processing tasks. Either case, probably a hardware issue.
In any case, perform a master reset of the Sync APIM and then run the APIM Interrogator Tool and post the results here. This can be done thru the Syn3 Updater (without upgrading anything) or thru the tutorial.
Tutorial: APIM Interrogator Utility - Ford / Guides & Info - CyanLabs Official Community