Here's a problem that I've run into playing solo or with another person in the Challenges area. When I complete a one or two star challenge, it won't unlock any of the weapon upgrades that I'm trying to obtain. I know I finish the mission because it states that I've completed the mission. Anyone else having this problem?

Yes, I am. For me the solo 2-star challenges are impossible so I don't know if the solo 2-star rewards are unlocking. I did do Parkour 2-star, but thats because there aren't 5 all knowing AI trying to kill me. I gone online and have done 4 man 2-star escort challenges about 50 times since yesterday and completed it each time and still no 2-star rewards. Also didn't get rewards for the Be More Objective nor Tower Defense while playing online with 4 people.
I am admitting I svck against the AI and even on easy they rip me a new one, all my story missions completed so far were from online play.

I think you have to do the challenges solo to get the unlocks. My friend and I played 3 challenges about 8 times yesterday, and didn't get the unlocks. When we tried them solo, we got the rewards...

This, you have to complete them solo. Sorry, I feel for you on the difficulty - my friend had an extremely hard time playing it as well.

Might I suggest stopping for nothing? Only kill the bots if they get in your way, and try and find light-traffic areas to go through. Those two tips helped me breeze through the 2-star Be More Objective challenge.

I HATE this challenge. Especially when it gets to playing as Operative and installing the hack box, because there's no point to doing it if your AI teammates aren't smart enough to protect it anyways.

this.

Do it with a new character that way the bits only have lvl one abilities, it helps a lot

im glad that i got it at the first time playin the 2star challenge there had just been 5 secs left
friendly bots are realy stupid and enemy bots always attack in big waves.... extremly annoying

Honestly I didn't have much trouble - but that's exactly where my buddy kept getting wrecked, too. He said he'd die within 1-2 seconds of getting near the hackbox objective, and I believe him - he's usually better than me in FPS games.

Run an SMG with a drum magazine, and some heavy-hitting weapon as your primary. Then just try and stick to the second story catwalks, I found that there were less enemies up there. If that doesn't work, then I'll tell you what I told my friend: You got a screwy version. :brokencomputer:

Not having any issues with this only the MP is annoying as balls