Export Dialog Box not opening (LR Classic 11.1 on MacOS Catalina 10.15.7)

When I try to export an image form LRC the Export dialog box doesn't open. The popup menu appears and when I choose a preset or export as previous the export is done, but when I choose Export... (from the right-click mouse button or from the File-menu) nothing happens. 

System and software is fully updated (Lightroom Classic 11.1, MacOs Catalina 10.15.7

Thanks for your input.

Kind regards, John