500 error when posting and getting user route


I have recently deployed my React frontend to netlify. My backend is built with Express and MySql and is hosted on heroku. The app works initially, fetching the initial data. But when posting (signing up) a new user I get a 500 error. Also when logging in an authorized user I get a 503 error -

/signin:1 Access to fetch at 'https://fullstack-courses-app.herokuapp.com/api/users' from origin 'https://upbeat-poincare-b03bea.netlify.app' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
Data.js:28 GET https://fullstack-courses-app.herokuapp.com/api/users net::ERR_FAILED 503

Here is my app's URL- https://upbeat-poincare-b03bea.netlify.app/courses
And GitHub repo- https://github.com/DeanYRepos/Tree-House_Unit10

Thank you

Hi @DeanYRepos

The error I got in trying to sign-up was

XHR POST https://fullstack-courses-app.herokuapp.com/api/users
[HTTP/1.1 500 Internal Server Error 412ms]

This means the error is coming from the backend you created, not Netlify. You will need to check logs for the backend to see what the issue is.