I own few unused RB600A
Once updated (i.e. ros 3 to 4) they loose license
Is it possible to use these devices with level 3 or 4 license and upgrade to latest ROS without purchase one (they're old discontinued devices) ??

Thank you

Ask support how to resolve problem

Just figured out one must upgrade 3 to 4, 4 asks to renew automatically the license online (RB connected to internet).
Then 4 to 5 and 5 to 6 is straightforward.
Thanks

License can be updated also from late 3.x (I don't remember exact number, but it's something after 3.20).

Last time I did this was about 2 years ago and the license update servers were down. I had to generate supout and contact support to get new license files.
It's always good to backup old license as well as generate supout before upgrading just in case something doesn't work...