Connections to the SharePoint server are currently disabled because the project is in Offline mode

Error occurred in deployment step 'Uninstall app for SharePoint': Connections to the SharePoint server are currently disabled because the project is in Offline mode. To connect to the SharePoint server, switch to Online mode by setting the project’s Server Connection property to Online, and then try the operation again.

Solution:

Open SharePoint project
Select solution
Click F4
You will see: Server Connection
Select : Online

Save