Because of the spam happening lately on this forum (posted by some malicious bots), now only current members can create NEW topics. New users can still reply to existing topics.
To be an approved member, you will new to create and account, then when you will click "New topic", you should see a page with a link to request approval.
No need to reply to this thread anymore.
Sorry for the inconvenience, the other option is to post an issue on Github's
rtabmap or
rtabmap_ros (if ROS related) repos.
The current ~2300 users have been given permission to continue posting as usual.