Force Centered Beam does nothing

I am working with a piece whose texture is almost entirely a single embellished line moving between the two hands. I want this line to be displayed with cross-staff beaming, and I know the steps to do this, but the final step to force the centered beam does not work.
I start here:


Then I move the LH into the same voice as the RH:

Then I use ‘m’ to cross back into the lower staff:

At this point I want the beam in the center, so I use Force Centered Beam from the context menu. Nothing happens. Both parts are in Up Stem Voice 1.

What am I missing here, please?
Thanks.

I found this in another thread:

So I guess I’m out of luck for now.