PC Problem Finishing "a Helping Hand" Scenario

After dealing with three of the four engines, I turned to the fourth one, which sits on a turntable track and is to be moved to the front of a long consist to which other engines have already been coupled.
The instructions do not include aligning the turntable with this engine's track, but I knew enough to do that anyway.
I then followed all of the instructions for starting this engine, but when the time came to drive ahead the engine would not move. I took a couple of simple F12 screenshots of evident problem causers. The first is a yellow circle with an exclamation point in it that appears in the HUD:

The second is what looks like a warning light marked "PCS Indicator":


Since neither this scenario's instructions nor the only user manual so far available for TSW2 mentions these two indicators, I'm hoping someone on this forum can tell me what they mean and what has to be done to turn them off.
In other words, I need a helping hand to complete "A Helping Hand". Thanks in advance.

 

When the Pneumatic Control Switch (or PCS) is open, the train brakes cannot be released and the throttle controls are deactivated. To operate your train again you must reset the PCS.

You can tell if it is activated by looking for the PCS OPEN light being illuminated.

If there is an alarm such as the Alerter sounding, acknowledge it (Q Key, B button on your controller).

Once the train has come to a complete stop, follow these steps:

1. Set the Throttle to Idle
2. Set the Reverser to Neutral
3. Set the Independent Brake to Full Service
4. Set the Automatic Brake to Emergency
5. Wait for 60 seconds
6. Release the Automatic Brake and wait for the Equalising Reservoir / Brake Pipe to return to 90psi

While the Automatic Brake is releasing, you will need to put the Throttle in to Notch 1 so that the compressor can recharge the Main Reservoir.

Once the Equalising Reservoir and Brake Pipe needles have returned to 90psi, and the main reservoir has recharged to 140psi, put the Throttle back to Idle.

You should now be able to release the Independent Brake, set the Reverser and apply Throttle.