error occurred in deployment step 'Retract Solution': The language-neutral solution package was not found

#1
Run Powershell

#2
Ensure you have Sharepoint Powershell commands enabled
For that run following command

Add-PSSnapin Microsoft.SharePoint.Powershell

#3
run following command (Replace mysolution.wsp with your solution name)
(get-spsolution mysolution.wsp).Delete()

this helped to me.
If still not
then open your solution folder and delete files from bin,pkg and obj folders and do the above mentioned again.