Problem with creating internal flow volume

Hello, I have some trouble at creating internal flow volume with my model. My model is a clean room with 8 outlets on the top and 4 inlets at the corners. The flow volume did not work by choosing any internal seed face. Could someone have a look at this? A massive thank you to everyone replying.

Hi thanks for reaching out to us,

You cannot create an internal flow volume because your volume is already a closed volume, which is identical to the internal volume. Therefore please go ahead and use the geometry you have uploaded in order to set up your simulation.

Best regards