A level 4 tool will work for m21 lon. But id check all output boards in that rack. Could be a diff board causing that output to not come up. Does it blink high for a split second on your tool? Like 3u/3d input is high, but do10 output won't open door? What if you give it a 3c at that time? Go to motion tab i think then IOs. Watch DO10 there.

I have a customer describing what seems to be the same problem. Mine is a 96 vintage digital dc four-plex. Haven't been able to see it happen yet. I think its a hall call input board issue, 2 of my four have the hall call inputs. I've sat on this bitch for 4 hours last week, 2 different days and of course it didn't happen.