Legacy Application on IIS 10

I have a new Dell Power Edge server with 2016 server std. installed. When I was configuring the server I installed Windows Admin Center. The server has been deployed to a client that uses a legacy application that runs on IIS. The application has to be accessed using Internet Explorer. It will not function properly in other browsers. When I attempted to access the application I got a 503 error. I thought that Windows Admin Center might be causing the issue so I uninstalled it using appwiz.cpl. The problem persists. After trying other possible causes I have found this; https://superuser.com/questions/1426442/run-website-on-iis-in-server-with-windows-admin-center-installed which leads me to think that Windows Admin Center may still be the problem. I have run the provided commands on 443 and 80
netsh http delete sslcert ipport=0.0.0.0:443
netsh http delete urlacl url=https://+:443/
I still have the same 503 error. I have this legacy app running on other 2016 and 2019 servers and used one of them as a template to check the IIS settings. Windows Admin Center seems like the most likely cause at this point. Looking for advice on how to remove any residual configuration, or other ideas.