Please check the following:
– Is the SD card already full? You can check this in the menu Settings / Restart.
– Please check that it is not on the VNC viewer is. We use the TightVNC Viewer here.
If you can exclude all this, please go to the Raspberry settings and adjust your display resolution under the HDMI settings. Set a hook for HDMI Force Hotplug and select the HDMI mode.
Than reboot your device and try it again.