I found this post. This user had exactly the radio installed which interests me. And it looks like the Sync 3 is not started in his vehicle until he has made an update to Sync 3.4. Did I understand that correctly?
Maybe the Transit is already sending “newer” CAN messages. Through which an update to Sync 3.4 was necessary. Because only Sync 3.4 understood these messages.
Is it possible to send private messages in this forum? I wanted to ask the user if he could send me a CAN log 
EDIT
Btw. how do you connect a device DIRECTLY to ForScan? I connected the CAN pins of the radio to OBD pins 6 and 14 (4 and 5 to ground and 16 to 12v) but it says it can’t find the vehicle (which is logical). Do I have to operate ForScan in any other way with a direct connection?