Press to call lift (spoilers)

[Crimbly]

Hello all,

Perhaps I'm being a bit stupid but I am stuck at the part of Soma when you finally obtain the Ark.

Having called the lift and placed the Ark into it, I have made my way down to the Dive Room to carry on. However, when pressing the button "Press to Call Lift", nothing happens. All that I've noticed is that the middle button for the central area is lit up white. Having checked a walkthrough, I should simply be able to call the lift - is this a bug or am I probably missing something?

Thanks in advance.

Crimbly