Hi! I understand you're having trouble getting logged into the updated Paychex Flex app on your iPhone running iOS 16.6.0. You mentioned the app loads after entering your credentials but never completes the login, and the help links just redirect you back to the app. Let's work through this together.

First, let's try the following steps in order:

1. Restart the App: Fully close the Paychex Flex app by swiping it away from the app switcher, then reopen it and try to log in again.

2. Check Network Connection: Ensure your iPhone has a stable internet connection. Try switching between Wi-Fi and cellular data to see if the login progresses.

3. Clear App Cache/Data: iOS doesn’t have a direct cache clear option, but you can try deleting the app and reinstalling it from the App Store. This often resolves any corrupted files causing login loops.

4. Verify Credentials & Reset Password: Double-check your username and password. If unsure, try resetting your password via the Paychex Flex login help page here: https://www.paychex.com/support/paychex-flex-reset-login-credentials

5. Update iOS: Although iOS 16.6.0 is recent, make sure your device is fully updated under Settings > General > Software Update, as sometimes newer app versions require the latest OS fixes.

If after these steps the login still doesn't complete, there might be a technical issue on the server or app compatibility. You can also check the Paychex support page for any reported outages or service interruptions: https://www.paychex.com/support

Would you like me to guide you through any of these steps in detail? Or if you have already tried some, please let me know which ones so I can suggest further actions.