I've noticed that when I remove (close/disable) an MT service, then add (enable) another one, not the same, its suggestions are not shown in the Matchboard in the current session, while "Show machine translation" is enabled.
Can you reproduce this on your end or do you wish to receive more input?
> Can you reproduce this on your end... ?
Yes, I can. Matchboard MT resources are set (or refreshed) when you switch from Dashboard to translation view. In the current session, you should be able to refresh them manually by changing the order of MT results in the Matchboard (first or last, and back to your preferred order).