Getting either a CORS issue or a Cloudflare challenge when trying redirect to authorize with OAuth2?

I am trying to redirect a user to login with their patreon and to obtain the code needed to retrieve their access token by using the following code in python (flask framework):

 auth_url = 'https://www.patreon.com/oauth2/authorize?response_type=code&client_id=' + client_id +'&redirect_uri=' + redirect_url
 redirect(auth_url)

When I try this I am getting a CORS issue on the frontend.

So then I tried this instead:

  auth_url = 'https://www.patreon.com/oauth2/authorize?response_type=code&client_id=' + client_id +'&redirect_uri=' + redirect_url
  return(requests.get(auth_url, allow_redirects=True).text)

which gives me a Cloudflare challenge page (without the CAPTCHA visible, so its essentially unusable) instead of the Patreon login page when the html/css/javascript text that is returned is loaded in the browser.

Any help would be really appreciated, I understand the Patreon API does not support CORS client side, but the redirect (302) is occurring server side, so the first should work correct? And in case the first doesn’t work, why is the second one asking me to deal with a CAPTCHA challenge (which is not fully visible)?

Thanks for the help in advance!

Are you loading or using any scripts in an iframe during the process? Or any 3rd party site or a domain not related to your app kicks in during the process?

For the frontend I am not using any iframes, but I am using jquery and bootstrap, just standard cdn links in script tags to their javascript libraries but nothing else. In terms of the backend, no there are no 3rd party sites/domains interfering.

Anyone have any thoughts?

Is the redirect that is happening a full redirect to a given url at the same domain/subdomain where your app is?