Hi,
I have the same problem but when using the rbdbulletsolver sop. Not any of the force-guides show up when toggled on or off.
I am able to show them when doing the following:
When going into your vellumsolver/rbdbulletsolver, up top where the "breadcrumbs" or "adress" shows you where you are, you can see that you actually jumped an extra layer deeper. A dopnet is suddenly extra there. That's normal because how those nodes are build up, but if you enter that dopnet (click on it in the breadcrumb-thing), you enter a "locked off" dopnet and suddenly the guides are visible in the viewport, at least if you toggled them on on your force. If you now pin your viewport to that view, you can go back to the forces and adjust them.
The so called breadcrumb (I'm sorry, I don't have a better word)

So it seems that the toggle or view of the forces gets lost in the whole dop-setup that simplifies the rbdbulletsolver and vellumsolver.
edit: I am on version 21.0.440 on Linux.