Stucked at Tri-Towers mission

Hello,

I was just doing first Crew Challenges at Tri-Towers, while my game crashed, and now, I'm stucked at "Play both Crew Challenges in Tri-Towers 1/2".

I have completed them numerous times, also in co-op, when I've invited skaters to my party (sadly, I don't have anyone to invite me.) - I've been spamming the "Party up?" and "Co-op challenge?" messages, but no one ever reacts to them.

Thank you for any tips and help.