Check the resolution settings on your source device and select a 1080p or 720p resolution.
There is more information on setting dual monitors with Windows 10 in this Microsoft Support article: Setup dual monitors in Windows.
Some devices, such as a computer or laptop, must have a secondary display setting setup in order to output a signal to the projector.How can I tell if my source device supports HD video output?.To connect you would need a compatible Wireless HDMI adapter (like a Chromecast for example). For example, the Samsung Galaxy S7, Samsung Galaxy S7 Edge, Samsung Galaxy S6, Samsung Galaxy S6 Edge, and the Samsung Galaxy Note 5 do not support HDMI video output with a wired connection.Some devices to not support HD video output.The source device connected to the projector is not outputting a video signal, or is outputting a video signal that is incompatible. If you are attempting to connect a source device via VGA, double check that you are using a VGA to HDMI converter, not the more common HDMI to VGA adapter which will not convert your analog VGA signal to the Digital HDMI signal required by the projector.Check that you have the USB-C cable plugged into the USB-C port on the projector that is labeled USB-C Video and not the USB-C Charge port.The cable has "USB-C Video Cable" printed on one end.