Get the latest stable release, and see if it still happens. If it goes away, it means someone else reported it and got it fixed a long time ago.
You may want to search the mailing lists to see if someone else has experienced the same problem. If so, there is a good chance that someone else has worked through the process necessary to shoehorn the latest NUT version into your distribution (potentially with unofficial packages).
Some OS distributions contain old versions of NUT. If your hardware is newer than the NUT release, there is a good chance that support has not been added yet. Please do not tell us you have the "latest version for Distro XYZ" — even if the developers are familiar with that distribution, it helps others if you quote the exact package version.
check the release date on the version you have. If it’s more
than about 6-12 months old, there’s probably a newer stable tree
version out there. As development happens actively, be sure to also
check if a custom build from Git (usually using the master
branch
of NUT https://github.com/networkupstools/nut/ repository) has your
issue fixed by some kind soul already.