Do you have different FT addresses on your Mini, iPhone and iPad?
Using FaceTime http://support.apple.com/kb/ht4319
Troubleshooting FaceTime http://support.apple.com/kb/TS3367
The Complete Guide to FaceTime + iMessage: Setup, Use, and Troubleshooting
Troubleshooting FaceTime and iMessage activation
iOS: FaceTime is 'Unable to verify email because it is in use'
Using FaceTime and iMessage behind a firewall
iOS: About Messages
Set up iMessage
iOS 6 and OS X Mountain Lion: Link your phone number and Apple ID for use with FaceTime and iMessage
How to Set Up & Use iMessage on iPhone, iPad, & iPod touch with iOS
Troubleshooting iMessage Issues: Some Useful Tips You Should Try
Setting Up Multiple iOS Devices for iMessage and Facetime
FaceTime and iMessage not accepting Apple ID password
FaceTime, Game Center, Messages: Troubleshooting sign in issues
Unable to use FaceTime and iMessage with my apple ID
How to Block Someone on FaceTime
My Facetime Doesn't Ring
To send messages to non-Apple devices, check out the TextFree app https://itunes.apple.com/us/app/text-free-textfree-sms-real/id399355755?mt=8
How to Send SMS from iPad
You can check the status of the FaceTime/iMessage servers at this link.
Hi Tom, I just checked my three devices and they are all set to the same. Some time ago I had changed my main email account to an icloud account (same name but an .icloud.com extension) and tried to change my Apple ID to this new email address. I had the icloud email address as my Apple ID on the IOS devices but the Mac had a .comcast.net extension. The Apple ID on each device is now set to the .comcast.net extension which is my original Apple ID account. But I am still having the same problem. I turned on my FaceTime on my iPad and tried calling my email address from my iPhone. It says it is busy. But I can call from my iPad or Mac to my iPhone and it connects. I am confused.
Hi Tom, I got it to work. At one point after playing around with this I was not able to call my iPhone from my iPad or my Mac using Facetime. It said I was not available for Facetime. In the settings on my iPhone I selected "remove this email" which was my .icloud email address. The notice said that it would remove this email address from all my devices. I selected it then after a moment it showed the email address again in the settings. But this time everything was working. I can now call my Mac or iPad from my iPhone and it doesn't say I am busy anymore.
Thanks for your help,