Hi York lai,
We’re happy to provide some assistance.
Based on your original post, we recommend the troubleshooting steps via the link below since you cannot connect your Beats Fit Pro to your iPhone.
If you can't connect to your wireless Beats product - Apple Support
The article above will show you how to troubleshoot the Bluetooth connection between your Beats product and your iPhone.
With that being said, to perform the troubleshooting actions recommended by the article above, please read through and complete the steps in the section highlighted in bold black font.
We’re recommending the steps above because they directly address the issue you initially reached out to the community about, which is that you’re having difficulty pairing your Beats wireless earbuds to your iPhone.
If the original problem persists after trying our suggested troubleshooting steps, provide us with specifics on what you see for more help, and we will continue from there.
Thanks for using the Apple Support Communities.
Cheers!