I run a website for authors, and we were using an add-on that allows for multiple nested comments, which can be very handy vs. someone "replying" 4 pages down the thread. We updated Xenforo software and the comments disappeared! YIKES is right! The company that made the add-on basically said they were sorry, but they weren't going to update it, they were moving in a different direction, etc.
Ozzy47 of OzzModz came to the rescue. His company took the time to fix the add-on and the first time we installed it, it worked perfectly and all 17,000+ comments snapped into place!
You can trust this man to come through for you. I am living proof. I have well over 1,000 very happy members once again.