That happens if you have not yet received the .res file from the server.
HiTech
His mission is selectable in the custom arena, yet I got an error message when I hit the Download Mission button, so I'm wondering if there was a problem when it was uploaded. That doesn't explain why Jimson's mission is not populating though. What I'm going to do tonight is:
1) Edit a mission I already have on the server and re-upload it and see if I lose the ability to populate it, in an attempt to duplicate whatever happened to Jimson's mission. I was able to populate his a few days ago, then after he made a few small changes and re-uploaded it, we (he & I, possibly others) lost the ability to populate. I have put his latest version that isn't populating in the M.E. and everything looks good build-wise.
2) I will make a brand new mission and upload it, then check if it is able to populate.
Will post results late tonight.