You may need to align a switch/junction. Make sure all junctions are set properly to arrive at where you want to go. As stated above, when you get close to a junction it "locks" and you can't change it. Locking distance depends on your speed. So you may have to stop, or even reverse some for the junction to release. Once all junctions are set properly, see if the signal changes.
(Note: This changes based on sessions. Some sessions have "locked" junctions set to make you go places, some sessions require you to control all junctions, and on some you need to control "some" junctions. Sessions can be drastically different on how they operate.)
If you want to try another Kickstarter 2 session I have one you can download via Content Manager. You'll see it's a bit different in that it has no Navigation icons, but there's plenty of instruction to let let know where to go and what do to. On Content Manager, look for a Session named "Local Duties - TRS19 KS2" by 1611mac