Hello All,
We have the following architecture:
Machine A: ArcGIS Server & ArcGIS DataStore
Machine B: Portal for ArcGIS, & WebAdaptors of Portal & Server
Our portal & server is publicly accessible. Recently, we observed that we are able to access portal publicly however, on trying to access server manager publicly we get the following error as shown in the screenshot.

Things that we have checked
- Able to access server manager through internal/port URL.
- Made sure services of ArcGIS Server is running from services.msc
- Able to access REST URL of the services.
Further it was observed that when we try to access server & portal through the FQDN of the webserver machine on which WebAdaptors are installed, portal is opening successfully however, server is still not opening. Attached is the screenshot

On researching on this further I came across the following link : Solved: Reconfiguring WebAdaptor for Portal - Esri Community
It was solved by uninstalling & reinstalling webadaptor. Hence, just wanted to know if that is the only way to resolve this issue or there is something that can be checked. Also, if uninstalling & reinstalling is the only way would anything happen to the existing services published to the server site.
Any inputs would be great .