[OrcishDonut]

So, I'm playing along, happen to be in Act 1, go through several battles noticing Aard doesn't seem to work.  I finally notice the icon on the left-hand side of the screen for this sign is .... black-outed.  I go back several saves and find a point where the sign is blacked-out while I'm standing in Abigail's Hut, which is where I saved the game at.  When I step outside of Abigail's Hut, the icon for Aard regains its color, so I start experimenting.  What I find so far is:  The first time I meditate, I lose the sign - the icon becomes blacked-out again, no matter where I am.
Can anybody explain what I am seeing and how to get around this?

[*Tommy*]

Sometimes it blacks out and you can activate it when you get in dangerous location or situation by clicking it .

[OrcishDonut]

Yes, that was it, thanks very much.

[green_abobo]

same goes for all the signs.

when you go from a neutral area to a combat one, you have to click the hotkey for which ever sign you wish to use.