During the introduction tutorial for the 766.2 after one releases the brake there is a step to wait for the brakes to charge, this step does not complete regardless of the amount of time I wait. I can confirm this is the case on both Xbox Series X and PC.
This does the trick. Apparently, the game considers the brake system as not charged because the holding brake (activated by the open doors) puts pressure on the brake cylinders, and the game not only requires the brake pipe to rise to 5.0, but also the brake cylinders to drop to 0.0. Just remember to close the doors before you touch the brake lever, otherwise you won't be able to use any controls. Also, whatever you do, DO NOT activate the Sifa on this scenario. The game doesn't let you release the pedal, so after 35 seconds, the emergency brake will apply. You can prevent this by disabling the Sifa again, but you will sill continuously hear the warning tone, a loud beeping sound, for the rest of the scenario. Even completely shutting down the train and turning off the battery doesn't stop this. I just finished the scenario like that and let me tell you, it is not fun.
i love getting mad at tutorials (that get annoyingly longer each route for trains i've driven 1000x) and it all being because dtg fails to say the right steps. world-class game design, as ever.