Normally,
a. once you have created a mail merge main document, the toolbar is
displayed and the buttons are enabled.
b. the toolbar is not displayed when a mailmerge main document is not open.

Is it possible that someone has put the Mailmerge buttons onto a
non-mailmerge toolbar (i.e. so that they are available for a non-mailmerge
document, but would not be enabled) ?

Are you even able to open the "Mailmerge Helper" option and see what type of
merge document your active document is?

Peter Jamieson