Fixing deploymet error: The feature is not a Farm Level feature and is not found in a Site level defined by the Url

If you have a SharePoint 2013 site that was migrated from SP2010 but the visual upgrade was not performed, then it will be on SP2010 UI mode as you can see in Fig #1 below (unlike the case of a brand new SP2013 or after the visual upgrade as in Fig #2).

Figure #1 -  Sharepoint 2013 with SP2010 UI

Figure #2 – SharePoint 2013 with SP2013 UI

So in SharePoint 2013 site with SP2010 UI mode, if you are deploying a feature (for example a visual web part) through Visual Studio or PowerShell then the following occurs:

• The feature is scoped to "Site", and Activate on Default is set to true.
• Active deployment configuration is default\
• Solution will be added to farm
• Feature will be installed on farm, and feature files will be copied to features folder in 15 hive (\15\TEMPLATE\FEATURES).
• .Dll files will be deployed to GAC or local bin folder
• User controls will be copied to control templates folder in 15 hive (\15\TEMPLATE\CONTROLTEMPLATES).
• Feature is not added to site collection features page.
• Enable-SPFeature command will fail with error message:
  The feature is not a Farm Level feature and is not found in a Site level defined by the Url [Site Collection Url].
• The .webpart file will not be copied to Web Parts Gallery (_catalogs/wp) in target site collection.
• Web part cannot be added to any page.

Solution:

Use CompatibilityLevel parameter in Install-SPSolution PowerShell cmdlet to deploy the solution in either or both 14 & 15 hives:

Install-SPSolution -identity SolutionName.wsp -GACDeployment -CompatibilityLevel{14,15} -WebApplication https://ServerName.Domain.com

Also, you can apply the CompatibilityLevel parameter to Enable-SPFeature cmdlet to activate individual features in either or both hives.