Using Okta behid a load balancer like Azure Front Door

I have 2 sites that are the same, on different regions of USA. I need to set these behind a load balancer, and set the Load Balancer as the face to the public.
Each of the sites works just fine independently, but as soon as I URL of the load Balancer, (in this case Front Door), after login to the authentication server, it redirect me to one of the regional sites, (https://regionalsite/authorization-code/callback) and stays as a blank page showing the “authorization-code/callback” until the remove it, and then I get to the regional site, not the mail URL of the load balancer.
I have tried Azure Front Door, and Azure Traffic Manager, and got similar results at the end. The main issue is that there is no documentation on how to set two sites behind a load balancer.
Does anyone know how to come around this issue, or face a similar challenge, to share a possible solution?