I have a sharepoint hosted app with a workflow in visual studio, sometimes the when I build the app it shows only "Build Started ..." and nothing from on. I'm sure there is no build errors in the project. Even waiting 10-20 minutes does not show any progress. Cleaning the project doesn't work too.
Try checking permissions for app, instead of building it in visual studio you can use online napa tools if you are implementing it on Office 365. Try checking following links,