Same thing happening here (Macbook Pro, Mac OS Catalina 10.15.5). Icy opens fine, loads the images just fine but when I click the 3D button the program just crashes. Here’s the output when I run the app in the terminal (in case it helps):

Apple AWT Internal Exception: NSWindow drag regions should only be invalidated on the Main Thread!
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'NSWindow drag regions should only be invalidated on the Main Thread!'

*** First throw call stack:
(
0   CoreFoundation                      0x00007fff324cfbe7 __exceptionPreprocess + 250
1   libobjc.A.dylib                     0x00007fff6b2a75bf objc_exception_throw + 48
2   CoreFoundation                      0x00007fff324f83dc -[NSException raise] + 9
3   AppKit                              0x00007fff2f6f6ddc -[NSWindow(NSWindow_Theme) _postWindowNeedsToResetDragMarginsUnlessPostingDisabled] + 310
4   AppKit                              0x00007fff2f6de842 -[NSWindow _initContent:styleMask:backing:defer:contentView:] + 1416
5   AppKit                              0x00007fff2f6de2b3 -[NSWindow initWithContentRect:styleMask:backing:defer:] + 42
6   libnativewindow_macosx.jnilib       0x000000016b1f56be Java_jogamp_nativewindow_macosx_OSXUtil_CreateNSWindow0 + 382
7   ???                                 0x0000000112d286c7 0x0 + 4610754247
)

libc++abi.dylib: terminating with uncaught exception of type NSException