YouTube has changed its configurations recently. That is the reason why you can experience the ‘Captcha required’ error message.
First, we recommend you to download and install the last available program version from our website. Here are the updates for Free YouTube To MP3 Converter and Free YouTube Download.
If the new version doesn't work, follow the steps written below:
Below you can see how to delete cookie files and site data in Firefox: View the image
And here you see where to clear cookies and cache in Chrome: View the image
How to delete all cookies in Edge: View the image