Check the following points to help resolve the issue:

1. Confirm whether the TV has the proper power supply. Check the power cord connection and make sure that it is not loose and check if the outlet is properly plugged in or not.
2. Check the HDMI cable connection at both the ends- TV and Cable/Satellite box- to ensure that they are properly plugged in.
3. Try unplugging the power cable from the TV as well as from the Cable/Satellite box for 10-15 seconds and then plug it back in again. After getting power, check whether the TV is recognizing the source.
4. Make sure that your TV is on the right HDMI port. Your TV may have multiple HDMI ports, so resetting the HDMI connection may fix the issue. Refer to the user manual for resetting to the right HDMI port.
5. If the issue persists, reset the TV settings back to factory defaults to see if that resolves the issue. Refer to the user manual for resetting the TV settings correctly.