I've been working on a few different ones and all of them get to 7 and will not let me assign a doff to start the mission. I also have had this problem with Recruitment. It shows the mission avail, you go to set it and it won't let you assign an officer to complete it. It doesn't say I do not have the right officer or need something I do not have.
Also, the support missions are already populated and I've been running a few but, I thought the additional aid missions aren't supposed to be available until after the last one in the chain is done?