Are you getting any kind of error? Or all of your worlds just in the core "Earth" sector? Sectors can be very large in the mod because there are so many hyperlane connections. You can't manually manage sectors in Stellaris anymore, if you colonize a new world that is too far from the core sector, it will then give you the option to create a new sector.

Im havig the same issue, all planets are under the frontier sector, when I open the planets and sectors screen I get nothing