It's already renewed and uploaded a while ago.

I highly recommend to use netxms-release package, which update keys automatically.

Key locations:
https://packages.netxms.org/netxms-keyring.gpg -- binary keyring
https://packages.netxms.org/netxms.gpg -- armoured key

Also it's available from key servers.

Make sure that key is not imported into trusted keys (e.g. using apt-key), but is stored in separate key store, as recommended in recent Debian/Ubuntu.