I think you need to enable the teamserver on your project: https://docs.mendix.com/developerportal/deploy/mendix-cloud-deploy

Hey snehal

did you create the project in Mendix studio pro or Mendix studio? If you created in the Mendix studio pro, you have to go to the Mendix apps in your developer portal and choose the project that you need to publish in the cloud , and on the left side menu, you can find the team server link open it and there enable it... 

Might this helps

A few things I think of;

1. Did you create the project from Mendix Studio pro or in the online platform?
2. Are you logged in with your Mendix account in Studio Pro?
3. Are you logged in with the same Mendix account you have joined the project?

Please provide a bit more insight in how you started & opened the project. Otherwise answering will be hard.

Did you, in the mean time, link a paid cloud environment to the application? 
The sandbox (which is the 'Run’ option) is free, but once you deploy the application on a paid cloud node, the option to run it in the sandbox becomes unavailable.

Is there still a free environment connected?

Follow these steps exactly;

1. Open projecyt in studio pro
2. click on the text balloons in in the control bar richt top
   
3. go to environments
4. Check if a free app is still connected:
   

If thats is true; I’m out of clues

If false; you or one of your team members unlinked the app