Obviously OP’s problem is long since solved (or not), but this was the top Google hit when I had a similar problem. My ribbon connector (for a laptop touchpad) wasn’t outright broken, but after being taken apart and reassembled it just wasn’t staying connected without my finger pushing down on it. It wasn’t so much broken as it was just loose.
Based on some other posts (people shimming ribbon/FFCs with various bits of plastic or cardstock) and some thinking, what I did was to take the ribbon cable out, cut a piece of electrical tape that was just the same size as the ribbon cable head, and tape it on to the back, the non-contact side. This makes the ribbon cable slightly thicker, so that when you stick it back in, the clamp is adding more pressure on the contacts. That fixed my problem, so I just wanted to document it somewhere on the internets in case it helps someone else.