Start idmapd at every boot

We suddenly had a "nobody" issue on NFSv4 mounts on SLES 12.5 machines.

The:

systemctl unmask nfs-idmapd.service
systemctl enable nfs-idmapd.service
systemctl restart nfs-idmapd.service
nfsidmap -c

solved it (+a correct /etc/idmapd.conf), but after a rebooot, we again have to start the idmapd service.

The question: How can we make the idmapd automatically start at boot?

UPDATE:

SERVER:~ # systemctl list-unit-files --type=service nfs-idmapd.service
UNIT FILE          STATE
nfs-idmapd.service static

From https://www.linux.com/training-tutorials/understanding-and-using-systemd/ I can see if a SystemD service is "static" that means it wont start at boot alone, maybe it has some dependency that starts it?