Hi there! I understand Avast Secure Browser is not starting up for you. Let's get to the bottom of this together. Could you please tell me if you see any error messages when you try to open the browser? Also, have you recently updated Windows or the Avast Secure Browser app? Any other symptoms you notice could be helpful.

In the meantime, here are some steps we can try to get your browser up and running:

1. Restart your computer: Sometimes a simple reboot can clear temporary glitches.

2. Force stop the browser process:
- Press Ctrl + Shift + Esc to open Task Manager.
- Look for any Avast Secure Browser or related processes.
- If you find any, select them and click "End Task."
- Try opening the browser again.

3. Repair the Avast Secure Browser installation:
- Go to Settings > Apps & Features.
- Find Avast Secure Browser in the list.
- Click it and select "Modify" or "Repair" if available.
- Follow prompts and restart your PC afterward.

4. Update the browser: If the app opens but is not stable, check for updates by clicking the menu (three dots at top right) > Help > About Avast Secure Browser. It will check and install updates if needed.

5. Uninstall and reinstall Avast Secure Browser:
- If none of the above works, uninstall Avast Secure Browser from Apps & Features.
- Restart your PC.
- Download the latest version from the Avast website and reinstall.

Do you have any cleaning programs or antivirus apps that might be interfering with Avast Secure Browser? Let me know what you’ve tried, and I’ll guide you further!

Are you comfortable trying these steps now?