The flap that clamps down the keyboard ribbon cable on my MBP crumbled, as well, while replacing the keyboard. I tried gently lift up the clamp and it went BLA. Tape, regardless of type, does not secure the cable tightly enough to provide a connection for the keyboard. Any ideas, besides tape alone, would be greatly appreciated!
Also, I discovered why the flap was so difficult to lift up. The ifixit guides leave our one very important detail. The back side (opposite the side the ribbon cable is inserted) of the connector is the only moving part and the only part that needs to be lifted up. The guides need to be very specific about this. Perhaps these instructions were clear in the ifixit guide, and I just missed it. Either way, it is a problematic scenario for those of us who have damaged our ribbon cable connectors.
Apologies for posting under "answer." This is my first time at this forum and could not figure out how to specify that I am adding to the question, rather than providing an answer.