Instrument editor - changing clef

I tried to change the clef in the instrument editor from treble clef to treble clef 8va below. As a result, the clef disappeared.
The project was created in Dorico 4 and I use Bravura. I am on Win 11.
I can’t post the (Multi-Flow-)Project here. But I can email it to Daniel or someone from the team, if it is needed.