I had this problem... If there were explodable things on the ground the objective wouldn't pop up till I 'interacted' with them.
Soon as that happened the objective opened up but I died
as I'd whittled down my health juping in the air on a barel when in wolf cloak
Reloaded a few more times, and the objective opened up as I spawned off the checkpoint reload and was able to get the 100% synch
Had me a bit confused for a while