Maybe the TV itself deleted the channel list, due to a software bug. Try rescanning for TV channels, but before that, make sure that the antenna is plugged in the TV.
Note: Most of the TVs offer you the opportunity to make a backup of the channels list to an external medium (USB, external hard drive, etc.). If your TV is one of them, make a backup (this option can be found under the channels section, in Settings), so that when or if this issue reoccurs, you can easily restore the channels list. If you are not sure whether your TV has this option, consult its manual.
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