Welcome to Apple Support Communities.
It's my understanding that you're unable to add your Apple ID to your second iPhone. I may be able to help with this. What is the exact error message? There's two possible scenarios on why you can't add your Apple ID, check out this link:
View and remove your associated devices in iTunes
Your iPhone, iPad, iPod touch, Mac, PC, or Android phone automatically associate with your Apple ID and iTunes when you use certain iTunes features. After a device associates, you can use it to download and play music, movies, TV shows, etc. that you previously bought from the iTunes Store. You can also turn on Automatic Downloads on an associated device.
You can have ten devices (no more than five of them computers) associated with your Apple ID and iTunes at one time.
The list of associated devices that you can view in iTunes is not the same as the list of devices that you're currently signed in to with your Apple ID. You can check your Apple ID device list to see where you're signed in on your Apple ID account page.
You don't need to associate your devices to buy content or download new purchases. You can remove an associated device if:
- You reach your limit of associations and want to add a new one.
- You can't download past purchases from the iTunes Store.
- You want to sell or give away an associated device.
Your iPhone, iPad, iPod touch, Mac, PC, or Android phone automatically associate with your Apple ID and iTunes when you:
When you try to associate another Apple ID with a device that was already associated, you might see a message that says, "This device is associated with another Apple ID. You cannot associate this device with another Apple ID for [number] days." Depending on when you associated your device with your Apple ID, you might need to wait up to 90 days to associate the device with another Apple ID.
Let us know if this helps.
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