Understanding what is the process of "secret base64 encoded" when user click on the tick button

yes, I know that but what I am facing. I have developed a code and successfully generated a token in my local area. but that token is not accepted by my third party API. check my first and second screenshots both token are same.
the same way I generated token from the JWT.IO website and tick the “secret base64 encoded” at that time token is creating different and I that token is correct which the third party API accepts. I am not sure what I am missing to creating a token like my third screenshot.

let me know if you have any idea.