I've been there myself when setting up a new device and hitting a roadblock during data transfer. One thing that often helps is making sure both your old iPhone and your new iPhone 15 Pro are running the latest iOS version. If there are any updates available, you can check and install them via Settings > General > Software Update on both devices. In my experience, ensuring both phones are up to date can resolve compatibility issues that might be causing the transfer to cancel.
It’s also a good idea to restart both phones. Sometimes a simple reboot clears up small glitches that can interfere with the transfer process. Additionally, make sure both iPhones are connected to a strong Wi-Fi network and plugged into a power source. I’ve personally encountered issues where a weak Wi-Fi connection caused the transfer to stop midway, and this could be what’s happening here.
Here is a more detailed guide: Apple Guide - Data Transfer Cancelled
If you’re still running into trouble, I’d recommend using a cable to connect the two iPhones directly. A Lightning to USB-C cable works great for this, and it tends to be more reliable than a wireless transfer. Alternatively, you could try restoring from an iCloud backup if the transfer keeps failing. Backing up your old iPhone to iCloud and then restoring that backup on your iPhone 15 Pro is a solid workaround that I’ve used when all else fails.
For more detailed steps on the data transfer process, check out this guide:
Apple Support – Transfer Data to New iPhone