If you have developed a custom web part using visual studio 2010 in SharePoint 2010, sometimes you will not see those web parts after deployment in the custom web part section. Here we will discuss how to resolve the issue.
If you have already developed a farm solution and want to deploy to SharePoint using PowerShell then check out this article
Coming back to our problem if you are not able to see your custom web part under Custom category then, one of the reasons might be because your web part feature might not be in activated stage. To check this Go to Site Actions -> Site Settings.
Then in the settings page, click on Site collection features under Site Collection Administration section.
This will open the list of features page, search for your web part feature (custom one which you have created and deployed). If it has not been Activated, please Activate that and check now the web part should appear under Custom category.