Got this message today on a new install of Web Access on a Windows 10 Dev workstation after the latest terrible Windows update. Not sure what it means since the error is blank but got lucky and found a workaround from someone else who had the same problem with another app. Had to go into the web.config and remove the entire <rules> section. Thought it might be helpful in case someone else runs into the error. Thankfully its just a dev station but I am not sure how critical the rules section is.