If you find that TPE or TPT (or any other iOS app for that matter) appears to be stuck in an install or update cycle that never completes, here are some troubleshooting tips:
- Try shutting down and restarting your device and then retrying the update
- In the device Settings screen, under iTunes & App Stores, confirm that you're signed in correctly with the same account used to purchase the app you're trying to install or update.
- If the above steps don't help, you may wish to try downloading the app in question to iTunes on your Mac or PC, connect your device and sync it to the device from there (see here for details). (From user reports, this has so far always resolved the issue.)
Unfortunately, this seems to be a relatively common issue that can affect almost any app - a web search will turn up a variety of other suggestions on handling the problem.