I've been playing Ghost Recon lately. Bugs galore!

I’m currently stuck on Mission 5. You have to knock out a tank to pass through to Mission 6. Or at least I think you do since I’ve been to the roof top with my squad but no helicopter ever shows up. The only enemy in sight is the tank. So I have got to believe that it’s the problem. However, when I set the explosive, it refuses to blow up. It blows up in the training session but for some reason it does not here. I must be missing something but what I haven’t a clue.:cry: