What to do if the Pi won’t give out video or the video is in the wrong aspect ration or resolution. First try powering off, unplugging and replugging the HDMI lead. This seems to fix it magically when no amount of rebooting will.
Also try swapping the HDMI at the TV end then replugging everything and reboot.
If that dont work try this
Power off, take out the SD card look in ‘config.txt’ and try adding this:
config_hdmi_boost=4 hdmi_force_hotplug=1 hdmi_drive=2
Because the config_hdmi_boost,
Configures the signal strength of the HDMI interface. The default value is
0 and the maximum is
The default value for the original Model B and A is
2. The default value for the Model B+ and all later models is
If you are seeing HDMI issues (speckling, interference) then try
7. Very long HDMI cables may need up to
11, but values this high should not be used unless absolutely necessary.
official docs and all video config modes here