He does that a lot. You either forgot to accept the mission, or you just need to try talking to him again. He gets messed up when multiple pilots are talking to him at once.
You may need to first remotely finish a mission that is in progress with the prior agent - the mission sequencing is a little odd and doesn’t well describe the resolution steps on some of the arc missions.
If you remotely accepted the mission from Sister Alitura, the server and client may be out of sync. You can usually fix this by clearing the cache (ESC menu, Reset Settings tab) or by logging off and back on. If that doesn’t work submit a support ticket and the GM’s will reset the mission for you.