How to Troubleshoot When iPhone Quick Start Doesn't Work

When switching from one iPhone to another, one method for data transfer is Quick Start. This method transfers data via Bluetooth, and the operational steps are simple; however, I wasn't able to get it to work. If the software isn't the latest version, the procedure for data transfer will only work after updating, and in my case, the software update took about 10 hours and still hadn't completed.