Is there something I have to do before hand? I save the fuel lines of the station, and I notice that there is no other squadmates.

There should be 3 mandalorians (Mandalore and 2 others), so that's an indication. What mods did you ran? Do you use a savegame from before entering that module?

I saved before I fought Atris as back up, I uninstalled any other mods so now all I have is the M4-78, and Restored Content mod. I replayed it and it only came up with two mandos, Zuka and the other one. Though when the Onderon troop said the rest of the group were going to advance to the fuel depot, I cleared it out and none of them appeared.

I had used other mods such as the Easy Influence Mod and Ebon Hawk inner textures. I uninstalled them and restarted that whole sequence, still nothing.

Did Mandalore appear when leaving from Grenn at the start of the Telos Revisit section?

No actually, there was no sight of a guy named Mandalore. When I got back to Telos, it was the Handmaiden VS her sisters, then her facing Atris. After that, my character appeared and I fought Atris. I got to Handmaiden, found her real name out and then the next thing I know, I am at the Citadel Station. All the cutscenes and such, nothing about Grenn or anything.

Replaying the whole thing now, I was beaten by Atris as Handmaiden and when I tried to reload it my character came in after Atris electrocuting her. I suppose that was intended. Yeah, never met a Mandalore.

Did Mandalore appear on Dxun? Did you pick him up there as party member?

Dxun?