I think I confirmed that this issue is related to the 3D view being in a separate window. I was able to get it to open my file by changing the 'com.eteks.sweethome3d.swing.HomeComponent3D.detachedView' property from 'true' to 'false'.

<t>Thanks for your suggestions. I just tried that, and the demo, saved somewhere else and re-opened, opens without a problem. <br/>
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I'm using 2 screens, BTW. My floorpan has the 3D view in a separate window on the 2nd monitor. So, I did the same thing with the demo file and moved the 3D view ...

I recently upgraded to the latest macOS 14.2 beta, and since then I can no longer open my .sh3d floorpan. The app simply hangs. The same file opens in SH3D on an older mac running macOS Catalina just fine.

Has any body else experienced this?