Direct monitoring greyed out now but wasn't before

I have Cubase pro 11 and a Steinberg UR242 interface. I used to have cubase elements 10 and had direct monitoring switched on. When I try to switch it on now, it’s greyed out ! Can anyone explain what’s going on ?

I’m having a greyed out issue as well all of a sudden. Did you fix it?

I must have, sorry I don’t remember how. No-one replied here so most likely I just kept searching google until I found something. I started keeping a record of how I solved problems six months ago but this issue was before then.