Health boxes dont'work

Unsure what you're trying to say here, but regardless of that... What platform?

Hi by platform do you mean operating system - windows vista, the problem I'm having/ bug encountered is that the red health boxes when used don't recharge health as they should do.

Is this in multiplayer or singleplayer?

SIngle player

(Yes, by "platform" I meant, PC, PS3, or XBox.  So "Vista" answered the question.)

Once a "health box" (as you call it) is exhausted, it can't be recovered until either; a) combat is over, or b) Shepard uses medi-gel.

NOTE:  Shepard can carry only a limited quantity of medi-gel.  Once it's gone, s/he can't restore the exhausted health boxes during the encounter unless s/he is able to find some more.

They don't seem to work after combat.

I thought pressing the activation key once over the health box would increase health do you have to press something afterwards.

Pressing 3 afterwards worked, thank you so much I can now continue playing this awesome game.