Some TVs are unable to find TV channels when they are set to scan for channels manually, i.e. in the Automatic search mode. Try scanning for channels manually, by entering the channel's frequency in TV's channel settings.
You can obtain the channel frequencies by contacting the operator, or on their website.
Maybe they have temporarily switched off their systems, as part of regularly-scheduled maintenance or there might be a hardware defect they are not aware of. Call them on their customer support number and let them know about this issue.
If you are subscribed to a cable-TV operator and you are unable to find channels, you need to ensure that your TV is set to search DVB - C channels, because TVs are usually set to search DVB-T(2) channels, by default. You can change this in the TV's settings, under channel installation (or a similar phrase).
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