Hi Momo,
we can try the outlet of the fan case. What I would suggest (would have to test if it works though) is to add a momentum source as a substitute for the fan. Otherwise you would have to provide a detailed geometry which we neglect by just adding this source so would not have to add additional modeling details to your components.
For the meshing I simply switched from very coarse to coarse to make sure the surfaces get detected properly. Will share the project with you in a minute.
Cheers,
Jousef