ELECTRIC UNIT REFUSES TO MOVE Options

[Blue Train]

Hi to ALL
Would like to know why a "train" will not move after installing a new route and trying to run one of the act created with the route.
But if I go into the MSTS ACT ED and change the player loco to one of MSTS default loco IE: the CLASS 50 then the the train "RUNS"
This could be a lot of things but I need to start somewhere to get it going again.

Thank you

Richard
Port Elizabeth
South Africa.