WooCommerce Authentication Endpoint 403 Forbidden

Hello. New here.

I have a site I created on HostGator for creating a new integration with an outside app.

The Authentication Endpoint is supposed to look like this:

https://afcsteststore.com/wc-auth/v1/authorize?app_name=MY_APP_NAME&user_id=123&scope=read_write&return_url=SOME_URL&callback_url=SOME_URL

If I put that, exactly as it is, into the address bar in my browser, I get an expected message that says “Error: The return_url is not a valid URL”.

If I substitute any valid URL in my URL above, for example:

https://afcsteststore.com/wc-auth/v1/authorize?app_name=MY_APP_NAME&user_id=123&scope=read_write&return_url=SOME_URL&callback_url=https://anything.com

Then I get bounced to a HostGator 403 forbidden page.

Because I get the “error” in the first case, I can see the script is working, and everything is there as it should be. But when there’s any valid URL, or even an invalid URL, provided for either the callback_url or return_url, I get the 403.

Obviously permissions are not set correctly somewhere. But does anyone have any idea where, or how to get this to work? I’m at a loss.

Any help would be greatly appreciated.

Thanks!