Hi there! I understand you're having trouble with the Zoho Mail app not opening or working on your device. To help you better, could you please tell me:

- Are you using the Zoho Mail app on a mobile device or accessing Zoho Mail through a browser on your Windows 10 PC?
- If it's the app, have you tried reinstalling it already?
- If it's on the browser, are you seeing any error messages or is it just stuck on loading?

Knowing these will help me guide you more precisely. Meanwhile, here are some general steps you can try:

1. If you are using the Zoho Mail app:
- Close the app completely and restart it.
- Uninstall the app, then reinstall the latest version from the official store.
- Check if your internet connection is stable.
- Temporarily disable any firewall or antivirus software that might be blocking the app.

2. If you are accessing Zoho Mail in a browser (such as WebKit based browser used on Windows 10):
- Clear the browser’s cache and cookies. Sometimes old or corrupted data can prevent the mail client from loading.
- Try opening Zoho Mail in an incognito/private browsing window.
- Try another browser (like Chrome, Edge, or Firefox) to see if the issue persists.
- Ensure your browser is updated to the latest version.

3. Check if Zoho service is down:
Sometimes, Zoho Mail may have temporary server issues. You can check Zoho's status page or community forums for any announcements.

If you've tried these and the problem continues, please let me know the exact behavior you're observing, and we can dig deeper, such as checking account syncing or integration issues.

Are you satisfied with this initial guidance, or shall I help you with detailed steps for your specific setup?