Files that do not need to be installed manually can sometimes fail if your PHP memory limit is too low. Please read this.
Some plugins and themes are bundled with other ZIP files. You need to Download the item, extract it, then manually install the theme or plugin as you would with any other file.
Some premiums plugins don't allow updating unless you have a valid license key. To update, you need to deactivate the plugin first, then click Update. If that doesn't work, then try manually uploading the new version.
Some plugins will continue to ask for a license key but most will continue to work without the license.
Most plugins do not require a license key to use them unless they have checks coded into the plugin. Since the plugins we provide are not nulled, some features might be prohibited without a valid license.