In some configurations, especially where projectors are involved, the home screen of the UDP-203/-205 may not appear on-screen, but a movie will play as usual once a disc is inserted.
The reason for that is that the OPPO home screen outputs at a higher resolution than 4K content. This then causes the home screen to not appear when displays like projectors are incapable of processing that higher-resolution signal. Ordinarily, the default AUTO setting for video output should take care of that, but some older versions of firmware struggled to address this issue with some projectors.
We recommend ensuring that the firmware is up to date. If it is, and the issue still exists, you can change the resolution in the Setup menu (Video Output Setup > Custom Resolution) to suit your display's capabilities.