If the ribbon is still in decent condition for example you severed it with a razor then this should work.
Tape the damaged sections of the ribbon to hold them together as closely as possible. Flip the ribbon assembly over and with a razor knife scrape away the white insulation revealing the foil conductors. Do one conductor at a time.
Very low heat and very fast soldering is the trick. You can actually bridge the break with a section of wire-wrap wire which is very small guage. I suggest using a liquid flux on both surfaces and tin both the wirewrap as well as the ribbon and let cool down before soldering. Once you have continuity on all traces and no shorts between adjacent traces, take some 5 minute epoxy and apply over the repair to provide mechanical strength and insulation. Or just wrap a wrap of black tape once around. Main thing is no sharp edges poking through either the epoxy or the tape.
If you find the traces too close together for a neat job, solder every second trace then flip the ribbon over remove the tape and solder the remaining traces.
Hope that helps.