Windows laptop not visible as input source on ATEM

Hi, for a live production I want to connect a Windows laptop of a teacher to my BMD ATEM Studio HD Pro. Laptop has hdmi output, display settings is set on full HD. Connected to the ATEM through hdmi -> hdmi/SDI converter -> ATEM (because it;s a long distance I use a BNC/SDI cable. But the ATEM doesn't receive the signal als it does with camera's. Even not when connected only through HDMI to the ATEM, so without the converter. I changed the ATEM itself to all possible settings concerning resolution en progressive or interlaced to see if the settings don't match one way or the other, but no difference: no input form the laptop. The laptop DIRECTLY connected to the Smartview HD screen gives an image of the laptop-screen, so nothing wrong there. But I need to connect it to the ATEM-switcher. So when live-streaming I can select that laptop-screen as one of the inputsources I want to show on the programm. But I don't know where to look for discovering the mistake/solution. By the way: the laptop is NOT used for ATEM software, so I have nothing to do with IP adres (I use a MacBook for that part and that works trough IP connection). Somebody? Thanks already! Ted

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