I am encountering an issue with entering the Purchase Code in the settings

Hello, I have purchased a WordPress plugin from your team. However, after installation, when I go to the Echo RSS backend settings to enter the Purchase Code, the 'Register Purchase Code' button does not activate. The message above still shows: [This is a trial version of the plugin. Automatic updates for this plugin are disabled. Please activate the plugin from below, so you can benefit from automatic updates for it!]