See this troubleshooting article if Real-Time Preview in Dreamweaver does not work, or if Dreamweaver no longer displays the Real Time Preview.
When you push a file to testing or remote server, the Live preview displays an old, cached version of the file that you are previewing. This issue is seen when you edit the document in full code view, design view, or split design views.
When you view a document in Real-Time Preview, the latest changes are expected to be displayed in the preview. However, you see the old, cached version of the file that you want to preview.
As a workaround for this issue, disable browser caching from the Settings menu in your browser. Then, click Real-Time Preview. The preview displays the latest version of your file.