We have had similar reports from some other Apple users and in a review of server interaction, devices are in fact hitting the server but are not parsing valid data and, as a result, our server ignores the request and TPControl times out. We are not sure why those devices are experiencing the problem.
Although perhaps not ideal, the following process will resolve the problem, assuming that you know the TOKEN, TPC User ID (Email) for registration and have the Settings and UI file information available to commission the device:

1. Uninstall TPControl
2. Reboot the device
3. Install TPControl from the App Store
4. Register using the Token Registration process and when prompted that the Token is in use with another device, press SUBMIT again.
5. Recommission the Settings and UI file(s) - if already applied to the Token in TPCloud and enabled, you can use the 'TPCloud update' option in Settings for TPControl.