Unable to send text to another iPhone on same account
To address this issue I'd recommend checking the iMessage settings on both phones. If they're both using the same Apple ID for iMessage, they may have trouble sending to each other. Changing the iMessage Apple ID will not mess up anything else (like the Store, iCloud, etc).

To check it, go to Settings > Messages > Send &amp; Receive

A button at the top of that screen will show you which Apple ID is being used for iMessage. If they're the same on both phones, you'll need to sign out on the one you wish to change. To do this, tap the "Apple ID: " button and then choose Sign Out.



Then you'll be able to sign in to iMessage with a different Apple ID, existing or new. I hope this helps!