Okta generates 400 error when redirects are updated to https (443) on AWS VM

I have a Ubuntu 18 VM in AWS running Nginx and Gunicorn3 hosting a Python Flask small web app. the Flask web app connects to Okta for authentication. As in...user logins into web app, and gets redirected to Okta for verification. Upon verification, user gets directed back to the web app. All this works fine on my local network with both Okta and Keycloak using http and the same identical web app. However, when I update the redirects in Okta to use https, Okta ignores the https and uses http. I get a 400 error but when I manually insert the "s" into the URL, it works fine. How do I force Okta to uses https with my redirects? Thanks