The track might not be valid :) Make sure the 🏁 is green in the track editor, on your right. If it's red, it means the track could not be validated by the game - it's likely missing a piece somewhere, or it has an obstacle obstructing the circuit!
Yes it's a bug in track validation, i'm looking into solving it for the next update, among others! It's because the radar antenna / tall building interrupts all navigation as it is very tall, but it doesn't check if the interrupted navigation happens above or under the very tall object
