Farm solutions error

I am trying to restore a sharepoint webapp from dev to QA environments. Took a backup on dev , restored on QA and created a web app on QA and attached the DB to this web app. I am getting an error 

"Could not load file or assembly 'CalendarWebpart, Version=1.0.0.0, Culture=neutral, PublicKeyToken=645f0ffd8949f7b3' or one of its dependencies. The system cannot find the file specified. "

so I copied the wsp to QA and ran 

Add-SPSolution -LiteralPath D:\minicalendarwebpart.wsp

For some reason it could not find the wsp so I had to use the GUID

PS C:\> Install-SPSolution -Identity 61a80630-19af-4e43-90ce-9cbe7f7496cb -WebAp
plication http://portalsb -GACDeployment -CompatibilityLevel {14,15} -Force

I am still getting the same error

Could not load file or assembly 'CalendarWebpart, Version=1.0.0.0, Culture=neutral, PublicKeyToken=645f0ffd8949f7b3' or one of its dependencies. The system cannot find the file specified.

I uninstalled using 

uninstall-spsolution -identity SharepointProject1.wsp 

waited till it retracted and

remove-spsolution -identity SharepointProject1.wsp 

but I am still getting the same error.

Could not load file or assembly 'CalendarWebpart, Version=1.0.0.0, Culture=neutral, PublicKeyToken=645f0ffd8949f7b3' or one of its dependencies. The system cannot find the file specified. 

Any suggestions on how to fix this issue so I can load the site ,,

@R