Pre-flight planning map not letting me add waypoints to trip?

Trying to route a muti-POI trip over New York, but I can only set Arrival & Departure. Can’t add custom destinations.

It let me do it previously flying over Yosemite, but here when I added a stop, went to set the next one and it automatically deleted them.

I’m on Xbox SX.

Any help would be appreciated!

I posted similar earlier today. I see the same. First time I’ve tried doing it though, so not sure if it is a new issue