Error in IIS Manager, "This website cannot be started. Another website may be using the same port."
Defender Management Portal website is inaccessible. It is showing as Stopped in IIS Manager, and when attempting to Start it, receive the error, "This website cannot be started. Another website may be using the same port."
There is another website binding configured in ISS that is current using the same port.
Review the website binding configuration in IIS Manager. If there is another website that is already using the port in question, you will need to select a different one. If the Default Website in IIS is not being used, this can be stopped, so that it's default bindings can be changed.
Review the binding configuration for the Defender Website. If there is a duplicate binding (ie. Two separate HTTP bindings on port 80), this will cause a conflict and can also be the cause of this error message. In this case, delete the duplicate binding and restart the website. Once the duplicate is removed, this should resolve the problem.