You see the box without any sphere ?
Or you see nothing (only the "VeloceProd" logo ?
If you see only the logo : type shortcut CTRL + W to display the real time position module. if I remember correctly this module is not displayed by default, you must open it if you want.
For other real problem, please go to motecadd installation folder and delete the file named "bug_report.txt", then start motecadd and launch the game in same condition and wait the "bug". After that, send me the bug_report.txt file by email (enclose it) to : contact [arobase] veloceprod.fr