Hi there! I understand you're having trouble with the Dmanager app where YouTube won't open, and you can't download music. Let's work through this together.

To start, could you tell me a bit more:
- When did this issue begin? Was it after an update or something specific?
- Are you able to open other apps or browse the internet without any problems on your iPhone?
- Have you tried restarting your phone or reinstalling the Dmanager app yet?

In the meantime, here’s a step-by-step approach we can try to fix the issue:

1. Check Internet Connection: Make sure your iPhone is connected to a stable Wi-Fi or cellular network.

2. Force Close and Relaunch Dmanager: Swipe up from the bottom (or double-click the home button if your iPhone has one) to open app switcher, then swipe the Dmanager app off the screen to force close it. Then reopen it.

3. Restart Your iPhone: Sometimes a simple restart can clear up temporary glitches.

4. Update the Dmanager App: Go to the App Store, look for Dmanager, and see if there's an update. An outdated app might cause YouTube not to load properly.

5. Check Dmanager App Permissions: Ensure the app has permissions to access the internet and storage by going to Settings > Dmanager.

6. Clear Cache or Data (if available in app settings): Sometimes cached data can cause issues; check if Dmanager has an option to clear cache or stored data.

7. Reinstall Dmanager: If the above steps don't help, uninstall the app and reinstall it from the App Store.

Since YouTube is also struggling within the app, can you confirm if the YouTube app itself on your device opens fine? Or is it only within Dmanager that YouTube content won’t load?

For downloading music, is it specifically through Dmanager or another app? Sometimes, restrictions or policy changes can affect downloading from YouTube-related services.

If after these steps, YouTube still won't open within Dmanager and music downloads don't work, it may be related to app-specific issues or changes on YouTube’s side that affect third-party apps. We can then look into advanced settings or alternative methods.

Let me know what you’ve tried so far and how things look after these steps! I’m here to help you get this sorted out.