Can't open tears

[Rubicon]

I'm just past the bit with the wounded knee fight and Elizabeth just walked past the gate. She offers to open the tear and I can see it, but pressing F on it does nothing. What can I do?
I'm using Kubuntu 16.04.

[Undisclosed]

You have to use your activation key, normally it is E.

[Rubicon]

Originally posted by Lord Flamongo (R'hllor):

You have to use your activation key, normally it is E.

E for me switches weapons, F is my default use key. It doesn't do anything to the tear, although it works everywhere else.

[miklkit]

That is the first tear in the game isn't it? You need to press and hold down the key for a few seconds.

[Rubicon]

That did the trick, Miklkit. Thank you much!