Hello! Let's figure this out together. It sounds like you're facing an issue with your device not being authorized to connect to the WalkPrint app.

First, can you tell me if you have already registered your device with the WalkPrint app? Sometimes this error might come up if the device hasn't been properly registered or authorized in the system.

Here’s a simple step-by-step approach we can take:

1. Check Device Registration:
- Open the WalkPrint app and check if your printer is listed under 'My Devices' or similar options.
- If it’s not there, you might need to add it again. Follow the prompts to register your printer.

2. Reboot Your Device:
- Sometimes, simply restarting your iPhone can help clear any temporary glitches that could be causing this issue.

3. Update the App:
- Make sure you’re using the latest version of the WalkPrint app. Go to the App Store and check for any available updates.

4. Check Bluetooth Connection:
- Verify that Bluetooth is enabled on your iPhone and that your device is within range.

If you’ve tried all these steps and are still encountering the "device not authorized" message, it would be best to reach out to the merchant from whom you purchased the printer. They may need to assist you in registering your device correctly.

Let me know if you need further assistance or if these steps resolve the issue! Are you satisfied with the solution I provided?