@axelg
Please check your pages now.
You had the free dashboard page set as a child page of marketplace. It needs to be a parent page.
You also had the vendor dashboard (pro) set as a child page of marketplace.. It also needs to be a parent page.
Your shop setting and orders should be child pages of the old free dashboard page.
I have fixed these (made the two dashboard pages parent pages, switched the shop settings and orders to be child pages of the dashboard free) and saved your permalinks.
Please test with a vendor now by going to the Pro Dashboard (vendor dashboard) page and seeing if the links and pro dashboard are showing correctly now.