Why is the tv not finding channels when channels are scanned?

When you run a scan the TV changes to every channel and tries to tune in a station. that is why it takes so long. If your TV is only finding channel 4, I would guess that is the only station strong enough for it to pick-up. You should check and / or replace your antenna and or antenna cable. Then re-scan the channels. with a better antenna, it should find more stations.
Most older Tube type TVs need a converter to pick-up digital TV, if you have a converter, make sure it is plugged in.

You should not be getting any stations without a digital tuner TV or a converter box.

The FCC site says this:

The FCC established September 1, 2015 as the date for the termination of all analog low-power television service. Since that date, analog television should no longer exist in the United States. Until that time, LPTV stations were allowed to continue to operate their analog facilities.

A guess; maybe you are scanning Cable channels while on air? So, if you don't have cable TV conected, it won't pick any channel.

Where is your antenna hooked up? Thru a cable box? Direct to tv? Completely describe setup, maybe post photos

When you scan it does it actually find channels? If you are in a remote area or living in a basement dwelling it may not be able to lock down on any channels. Try going "outside" at about 2AM and try scanning.....and see if it locks on to any channels. Also, your antenna. Use a telescoping antenna that has at lease 8 links on it.

you can do the auto search channel. just press the tv menu and then find the channel search and select auto search. so that all available local channel will tuned.

If you try another TV does it pick up more stations?

I think you are confusing the channel on the tv and the channel of the cable company that is not something that you can pick up with the scan tv, scan tv is good for picking up local channel meaning air channel that we get with a antenna only not the cable chanel

if you have a cable box just plug the cable box into a scart socket on the tv, switch the tv to the scart input and use the cable remote to change channel?Scanning for channels wont find anything because you are receiving the channels on a cable box. If you are refering to standard or digital tv signals and your not receiving any channels then either you are only scanning analogue tv and therefore wont pick up any digital tv channels, or your ariel is inadequate to receive an acceptable digital reception and will need to be upgraded. please state country you are in and what you are expecting to receive

Have you been into scanning settings and set to DTV , it seems like you are either on ATV or have a bad Antenna connection. If signal is weak from your Antenna you can add a booster in the section between your wall socket and the TV. You cannot use Satellite dish connections to receive either ATV or DTV signals without a set top box ...

pick up the remote turn on tv....press menu...setup....tv....then channel scan....(note your tv should also be on cable broadcast not air)...hope this is helpful