Hi, there
There is no 'DirectX Input' any longer. It was replaced years ago with the current system (there were specific reasons why VA had two sets of inputs years ago, but it went away in version 1.6).
What we would need to see is the rest of the command - A 'press key down' should be followed by a 'release key' action (using the same key), as well as a small pause between the 'press key down' and 'release key' actions:
Press Num 8 key down
Pause 0.1 second
Release Num 8 key
You can play with that pause a bit (increase/decrease) to see what works best. The pause is necessary in games as they often work on a polling mechanism to see when keys are down. If there is no pause (or a pause that is too short), the game might not see the key being down as it is occurring too quickly. Just making an assumption here, as this is something that occurs a lot.
Hope that helps!
(If not, take a look at this thread, as it's helped many over the years):
https://forum.voiceattack.com/smf/index.php?topic=53.0