Looks like the link to the new Turbine DLC is broken https://live.dovetailgames.com/live/train-simulator/articles/article/turbine-triple-treat Seems it was forgotten to enter the actual URL.
https://store.dovetailgames.com/uk/...nion-pacific-gas-turbine-electric-loco-add-on For those looking for it
Same problem on the page below: https://live.dovetailgames.com/live/train-simulator/articles/article/famous-fast-historic As reported by Larwood in thread: https://forums.dovetailgames.com/threads/ts21-famous-fast-and-historic.32710/