There are many reasons why you could be having trouble receiving a certain TV channel. The signal could be affected by different types of interference including communications signals, LTE/Cellular, Microwave feeds, weather conditions, physical obstructions or reflections, etc.
Also, there could be times where the TV station transmission has been changed for some reason. The transmitter could be shut down while under repairs, or the station had to temporarily needed to reduce the transmit power. The Stations can make changes for up to 10 days without notifying the FCC. They can also reduce the transmit power to 80% of its normal output for up to 40 days without notifying the FCC. Temporary power reduction is more common with low power VHF channels. You can visit fcc.gov to further research this topic.
The links below go to some very interesting and educational web pages, about ATSC HD TV Signals/reception;
Please note; The 'HD Primer' site has not updated the UHF channel list since the FCC changed the channel highest channel to CH51.
These are not affiliated with Channel Master and we are not responsible for their content.
Another good source for technical info about possible causes for reception issues;
Another good source is otadtv.com