After installing Remote Desktop Services recently for a client we found the portal wouldn't start correctly and we were presented with error 500.19. The solution was to do the following courtesy of https://forums.iis.net/t/1149768.aspx -> Take IIS backup.
-> Open IIS
-> Click on server module node at the top of the left hand tree and choose "Modules".
-> Right click on DynamicCompressionModule and choose "Unlock"
-> Right click on StaticCompressionModule and choose "Unloc