Hi,
It has been a while since I used the map_optimizer node, there could be a regression error (I opened an issue
here). If you have more info about your setup/launch files, you can update the issue.
To know if the binaries are installed, you can list installed apps:
$ dpkg --get-selections | grep rtabmap
ros-indigo-rtabmap deinstall
"deinstall" means that the binaries are not installed. You can also look in synaptic.
The hydro binaries are stuck at 0.8. You can build rtabmap from source to use the latest version on Hydro.
cheers