Have you tried to commit or update recently? If not try to do that, because if the application is deployed correctly to team server repository, you should not have a problem here.
If this is the case have you tried redownloading the application and then deploying to the sandbox?
This issue is related to a hickup when projects were created resently. This has been solved already for a few days, but that doesn't help your current projects.
Best and shortest way to fix this is by exporting your project as package and create a new project/App using that package.
Step by step:
1. Open model in the modeler
2. In the main menu bar of the modeler go to: File > Export project package
3. Export it with or without local db, With, if you want to have your local data in the new app as well. (won't be pushed to the cloud database!)
4. Close project
5. Click Open app in "My Apps" tab
6. Select "Disk"
7. Select your exported package
8. Set nice project name and click ok.
So i downloded new copy from teamserver, same result.... Can commit, run local but not deply to sandbox ("Run")
I am also having the same issue. I can't get to the node list to see if anything is occupying the Sandbox node. Also, as in the other comment, the Run option is greyed-out in the Modeler.
Same problem for me. Tried work-around from Rene, but didn't give me a resolution..
Open for any suggestions.