I added the PTT service on my phone not thinking that my device may not yet be compatible with the app from AT&T. I found out the hard way but figured out how to get it going on my device.
1. After adding the service online I got a text a half hour later that it was active on the account.
2. I then rooted my Note 2 on the latest stock 4.3 rom.
3. Downloaded the app: Device Spoofer from the Play Store.
4. Backed up the device's current information in Device Spoofer
5. Changed the device's ID to that of the Galaxy S4 (i.e. sgh-i337)
6. Restart the device.
7.Launch At&t EPTT app and activate.
8. Once activated you can run spoofer again and restore your device's I'D and restart and the app will still work.
Just guessing but I would think this should work on the Note 3 as well. Everyone uses this at work so I thought it was worth looking into.
***EDIT: I used the Helium app to backup the At&t EPTT app and data to my Google Drive account and restored it on my At&t Note 3 and can confirm it works. I did not root my note 3 due to the Knox issues discussed here on XDA, so if anyone has another device that is rooted this is an easy way to get the PTT app working on a non rooted one.***
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