Why would an DSI MIPI HDMI device accept Windows 10 HDMI signal but not HDMI signal from a GoPro or wireless HDMI transmitter?
There are two possible reasons I could see for this.  The first is that the supported resolution information is not being properly sent, resulting in a signal being sent which is not supported by the display.  It is also possible that the GoPro and the wireless HDMI transmitter do not support the same resolutions as the display you are using, in which case it wouldn't be able to send a workable signal.

The second possible issue is that of HDCP.  HDCP is a technology used to protect copyright video data when it is being displayed.  If one of your source devices only operates with HDCP compatible devices, it is entirely possible this display is not HDCP compatible and that would prevent the display from working as well.