Likely a compatiblility issue between the recorder and the TV. The user manual states unsupported resolutions will be skipped. It is also stated several times in the manual that not all HDMI connected devices function correctly together. This is caused by different implementations of the HDMI spec and HDCP.
Also, HDCP implementation on many devices prevent the upconversion of copyrighted material. So assuming you are testing with store bought DVD’s, it is likely an HDCP restriction.
Regardless, your TV has to up-convert the incoming signal anyway to match it to the native resolution of the screen. So you are only at a disadvantage if your DVD player has a better scaling chip than you TV, which is highly unlikely in your case.