I was trying a 6th order design. When designing a port is shown in front chamber. In rear chamber i cant place one. When a surface is clicked upon a opposite one lights up green. This goes on till all light up except the one i want the port in. And then the app shuts off automatic. When i try to place the port on a surface i dont want it to go when it lights green. It shows no port. I have no problem designing other types of boxes and am using pro app for some time now. I hope this helps.
You have to design your ports separately for each chamber: by clicking on buttons "front chamber" and "rear chamber" on "port" tab - maybe this is the problem: you did not filled in the dimensions for the rear chamber's port. If at 3D designer you have just 1 port, not 2, probably this is the problem.
The other thing which can be a problem is maybe your port have too big port area to install it on tat surface which you have chosen... or something similar problem with some dimensions.
Third: with SBL you can design only parallel tuned 6th order bandpass boxes.
As I understand, you try to place the port on the chambers divider, and then the app crashes? Do you use iOS or Android app?
I use ios on my ipad. It somehow works now. So that’s a plus. Thx for the help.