ArcGIS Enterprise 10.9.1, We are trying to install Web Adaptors for Portal and Server. when i try to install 2nd instance of Web adaptor for server, It is showing either repair or remove the webadaptor from the system. Why it is not allowing us to install 2nd instance of the web adaptor on 2019 Datacenter edition?
Have you met all the dependencies of the IIS install? I'm assuming so as 10.9.1 should prompt you to deploy all roles (IIS Components). Is anything else on the web server other than Esri, or is it a fresh install of IIS?
it did not prompt for any IIS dependencies. it is a fresh installation.
Have you tried using a different context name instead of Server? At this point, I think you need a call with Esri Support to guide you through this. I often call my first server 'Hosting' instead of Server, as typically that is the role that machine fulfills. I honestly don't think it will make a difference, but maybe worth a try before going to Esri support.
I have always called the server web adaptor - arcgis, and the portal adaptor - portal. It keeps things simple.