After creating a custom form feature you discover that you cannot add it to your custom form and activate it. You tried adding Group Features, but could not find a way to activate your Custom Form Feature to your custom form.
This issue can occur when the custom form has required values that are empty. The Cannot Click The Save Button Upon Making A Change article explains how this happens and how it can be resolved. Complex custom forms may need to be rebuilt a little at a time to determine the exact component/content that is responsible for the feature becoming inactive when the form is enabled.