Could please explain what you mean?
"moving" a message always means copy it to the specified folder and delete
it in the source folder.
These rules worked before, as they are defined. No changes, such as
reselection, should be necessary
I agree, it should not be necessary. However that does not mean that
something hasn't gone wrong, in which case reselecting them can sometimes
cure the problem. Have you tried it?
I also discovered that if I select a message and apply all rules, nothing
happens even when that rule that should affect it is first in the list. But
if I select the same message and apply the rule that should normally affect
it, the rule has the intended effect.
I conclude that something is preventing the rules from being applied
automatically.
That would imply that a rule earlier in the list is catching the message
first. Try to disable all rules before the one you want to apply to a
p[particular message, then try the 'apply all rules' trick - does that rule
now work? If so, start working your way through the list to see which is the
rule blocking the others.