I have seen that when there is a port conflict. While it should tell you, sometimes it doesn’t Try assigning a different port…
Also, in the …/deployment/log folder there are logs. You might find something there.
Did you tried cleaning the deployment directory ? Goto App--> Clean deployment directory and try running it. Let me know if it works.
After lot of trial and error, I found the way to resolve the issue myself, atleast temporarily.
This seems to be an issue in Modeler which is confirmed by Mendix Support also.