When I choose:
View -> Filter -> Categories -> Personal -> Health, the category selection window closes and when I go back by retracing my steps, Health is not checked. Moreover, sometimes the filter does not change anything appearing on the screen, so in these cases I infer that the filter is not using the category. This happens with whatever category or categories I try.
I have tried this using the same file on two different computers. On one the filter has no effect on the tasks I see. On the other it does filter tasks, but there are no checkmarks by the selected tasks, and there's no way to turn off individual categories as part of the filter.
I can't reproduce this. Could you attach you TaskCoach.ini file as well as your anonymised task file (see Help menu) ?