I exported all flows, and Deployed on my new install. But my dashboard is totally empty. How can I get back my original dashboard ?
Have you reinstalled the dashboard node?
EDIT: And all other nodes of your former installation, of course 
What do you mean by totally empty? No widgets or no background or what?
Are your flows present in the editor? Can you see the dashboard nodes there?
I have the message "Welcome to the Node-RED Dashboard Please add some UI nodes to your flow and redeploy". I have about 15 different flows and have 5 pages of Dashboards
If I click on any dashboard type nodes (like a TEXT, GAUGE or LEVEL) they all have their Dashboard Groups, but yet the UI Dashboard shows nothing at all
Within Dashboard Layout, all Tabs & Links are all present, and my original colours are within the Theme section. But within Tabs & Links, if I click on Layout to Edit the layout, it's all blank
Stop node red and start it again in a terminal and copy/paste the startup log here. Possibly it will give us some clues about what is going on.
