How to fix “A deployment or retraction is already under way for the solution “*.wsp”, and only one deployment or retraction at a time is supported”
I faced this issue when I try to deploy a solution and it failed initially due to SharePoint 2010 Administration service is not started. I then started the service and redeploy the solution; however I face the above issue. To fix it, you need to cancel the current deployment then redeploy the solution.
To fix it, you need to cancel the current solution deployment. Go to CAà System Settings àManage farm solutions and then cancel the deployment. Next, you can redeployment your solution.