If after a 2019 Microsoft Office (Word) update you notice that when you generate new Medilink letters it just seems to stop, please go in to File Menu -> General Options, and uncheck Show Word During Merge (see screenshot below).

For some users this Microsoft update is resulting in Word staying running and therefore not 'telling' Medilink it's finished creating the letter. However, changing the level of display of Word (i.e. to run it in a more 'silent' mode) seems to resolve the problem.