We recently started using database project in our application. To get the updated stored procedures from database project to destination database we were using "Build" option. The issue with this option was that it was not importing new stored procedures from database project to destination database. The fix for this issue was to select "Publish" option.
Right click the database project and select "Publish":
After that select the datasource and click "Publish" button.
After that we noticed all the new stored procedures were imported into destination database.