While updating a wsp in SharePoint 2013 environment I got an error saying that “Cannot uninstall Language Pack 0 because it is not deployed when attempting to uninstall-spsolution.” As shown the image below.
By checking the solution in farm solutions (Central Administration -> System Settings -> Manage Farm Solutions) Solution wasn’t deployed. I have found this blog explaining the issue. The reason for this error is that DLL’s in the GAC were not able to delete. So I have deleted the DLL’s in the GAC and deployed through SharePoint central Administration
If it is timer job, We have to Stop and SharePoint timer services in the services.
Hope this helps.