Need to lower the second bridge

[DennisGG]

If you haven't done all 3 puzzles in the Machine Room, pulling the lever should say something along the lines of "There's no power".
Solution: Do the puzzles. If you're not sure if you've done them, go and check that you can't move any of the valves and levers in the Machine Room.

If you have done the puzzles, the bridge should come down a little and then get stuck. Pulling the lever should say something like "It won't budge".
Solution:

Spoiler below!

Interact with the bridge and you'll learn that the bridge is stuck and will need a push to dislodge. There are rocks around the place. Try throwing some at or on the bridge.

Thank you for the swift reply !