[Pan-users] Watching a thread

[Beartooth]

        I have at least one machine on which Pan (pan-0.146-2.fc32.x86_64) 
is perfectly amenable to watching a thread -- and at least two, identical 
afaict, on which the same procedure (right-click, run down the list, 
click "Watch thread") does nothing.

        I've gone into Edit Preferences and scrolled clear down; to the 
left of Watch thread on all three, the box contains nothing visible.

        How do I fix this??
-- 
Beartooth Staffwright, Not Quite Clueless Power User
Remember I know little (precious little!) of where up is.