Getting Invalid Tokin issue

When you get this error, it means that your token is expired or you are setting invalid data in token here:

https://github.com/basir/mern-amazona/blob/master/backend/utils.js#L12

and

https://github.com/basir/mern-amazona/blob/master/backend/utils.js#L29

try relogin please in your web app.