The inputs 1-3 on the VR-3EX only support 480P/576p. Input 4 supports up to 1080p. It's likely that what your sending out is a resolution higher than 480p/576P into inputs 1-3. Try them into Input 4 it should accept what you're trying to send in. You can read more about the resolutions accepted by the VR-3EX in VR-3EX HDMI accepted resolutions article.