3ds Max 2019 has introduced a bug which disables the interface of Maproom (and all other scripted .net interfaces for that matter). The script starts up, but all the buttons are disabled.
If you want to use Maproom in 3ds Max 2019 you should install one of the dates for 3dsMax 2019. Any of them will do: 2019.1, 2019.2 or 2019.3. These updates are available though your own autodesk account.