If your changes are not showing up within the Preview, try:
1. Refreshing the preview page.
2. Making sure you have selected all the necessary Save buttons after making changes.
3. Closing any other windows of the Dashboard/Design/Content panels that may be open.
4. Making sure that the changes you are making are being recognized in Content (a blue check mark will appear will the changes are recognized).
If you are still having issues, feel free to reach out to Support for further assistance.