Hey there tj_penny,
Thanks for reaching out to the Apple Support Communities.
If having issues with connecting your Nintendo Pro Controller with your iPhone, check out the steps in the following resource that can help with troubleshooting this issue: Connect a wireless game controller to your Apple device - Apple Support
If the controller doesn't connect or work as expected
Support for specific buttons and features, such as a controller's audio jack or lights, varies by controller and the app you're using with it.
* Install the latest software updates—both for your Apple device and the controller. If a software (firmware) update is available for the controller, get it from the maker of the controller.
* In Bluetooth settings, select the controller or the info button
(if present) next to its name, then select Forget This Device. Connect the controller again.
* Reduce the number of Bluetooth devices connected to your Apple device. This can also help with connection issues related to wireless interference. Apple TV 4K and Apple TV HD support up to four Bluetooth game controllers at the same time, or one controller when Apple TV is also using a Bluetooth audio accessory. The limit for other Apple devices varies based on your specific setup and wireless environment.
* To charge your controller, use the charging solution included with your controller or recommended by the controller manufacturer.
If still having issues after going through the steps above, you may need to reach out to Nintendo to confirm that the controller is compatible with your device. You can find ways to reach out to Nintendo Support at this link here: Support - Nintendo
We hope that's able to help.
Take care.