iPhone Calendar Search not working

Sorry for the delay in responding. I just tested mine and it seems to be working just fine. You do not indicate any troubleshooting steps you have tried. Generally the first one is to do a Force Restart on the iPhone. Here are the instructions for that. Force restart iPhone - Apple Support

What happens when you attempt to search for something? Is the event you are looking for in the past? If yes, how far in the past. I know that you can only search 12 months back.