In SharePoint 2010, you may try deploying or upgrading a solution using stsadm and end up with the below error.
A deployment or retraction is already under way for the solution “Solution Name”, and only one deployment or retraction at a time is supported.
This issue occurs if a SharePoint solution deployment fails, yet the timer job is created and not running, you will be unable to redeploy or retract the solution.
To resolve this error and redeploy the solution, follow the below steps.
- Go to Central Admin -> System Settings -> Manage Farm Solutions.
- Cancel the deployment for your solution. It may have the status failed or deploying, which means deployment is not successful.
- Now redeploy your solution.
Hope this helps .