Pocus, PhilThib, or Tamas should be able to assist you with this. I believe the AAR subforum links over to a different forum board, might just need permissions added. I'd love to see an AAR!
I can confirm the permissions on the AAR sub-forum are not currently set up to allow new posts/replies/etc. Could one of the forum moderators investigate?
I believe this was done before to protect this sub forum for being overwhelmed / spammed. Could you try posting your AAR inside the WW1 forums and check if it works?