Hello! I see that you're having an issue with the PBS app on your Roku device not starting after entering the activation code. Let's work through this together to get it sorted.

First, could you tell me a bit more? For instance:
- After entering the activation code, does the app freeze, crash, or go back to the home screen?
- Have you been able to successfully activate the app before on this Roku device or is this your first time?
- Also, have you tried restarting the Roku or the app itself?

Meanwhile, here are some initial steps we can try:

1. Restart Your Roku Device
Sometimes a simple restart can fix temporary issues. You can restart by going to Settings > System > System Restart, or simply unplug your Roku from power for about 30 seconds and plug it back in.

2. Remove and Reinstall the PBS App
Try removing the PBS app and then reinstalling it. To do this:
- Highlight the PBS app on your Roku home screen
- Press the * (star) button on your remote
- Select "Remove channel"
- After removal, go to "Streaming Channels," find PBS, and reinstall it.

3. Check Your Network Connection
Make sure your Roku has a stable internet connection. Sometimes connectivity issues can prevent the app from starting properly.

4. Activate the App Correctly
When prompted, you should enter the code at pbs.org/activate exactly as it appears on your Roku. Ensure you're logged into your PBS account when activating.

If after these steps the PBS app still won’t start after entering the code, there might be an issue with the app or network settings like router blocking certain PBS services, which sometimes cause the app to crash or return to the home screen.

Let me know what happens when you try these steps, or if you need guidance on any of them. We'll get that sorted for you!