I have an APC smart UPS 3000 RM connected with a genuine APC smart ups cable.
I can dialog with the UPS properly trough the '/system serial-terminal serial0' ROS command.
However, when I am trying to add this UPS to ROS I have 'Couldn't add New UPS error - opening serial port failed: 2 9 (6)'

This UPS is properly managed when connected to a linux server with apcupsd.

I'm using a RB1100AH with ROS 5.20

I've seen other threads with people having issues with 5.20 with their UPS. Is it a bug and will the Smart UPS 3000 RM be properly managed in the next release, or should I forget using my router to monitor the UPS and delegate that to one of my server?

Search this forum. In 5.20 is UPS package unusable. Downgrade to 5.19

http://forum.mikrotik.com/viewtopic.php?f=2&t=64785

doesn't work with 5.21 either. Now the UPS shows as invalid.

Very good, very good ... One small step for man, one giant leap for mankind. In 5.67 will be fixed.

doesn't work with 5.21 either. Now the UPS shows as invalid.

Sorry. In 5.21 serial (RS232) UPS working well.