According to the specifications, https://www.cnet.com/products/hitachi-l32a403/specs/
, the Hitachi L32A403 has a digital (ATSC) and an analog (NTSC) tuner. Check if the input/source is set to TV. The signal strength information will only be available if you are using the digital tuner. This TV has an Input button on the TV and on the original remote. (It's the second from the bottom on the side of the TV, between the power and menu buttons. On the remote, the Input button is above and to the right of the arrow/Select keys. The Menu button is on the left side of the remote in that same line.) Press the Input button and then use the arrow keys to highlight the desired input; press Select to go to the input. On the TV the Channel Up/Down buttons are the same as the Up/Down arrows on the remote in this menu. The Volume keys will work as Left/Right.
Make sure to set the Channel Source to Air before attempting to scan for channels and check the signal strength. The Channel sub-menu is at the bottom of the list on the On-Screen Menu, after you press that button. However, this menu is not available if the input isn't TV. See the manual here: https://www.searspartsdirect.com/partsdirect/user-manuals/l32a403-hitachi-parts-manual
Since digital signals are either enough to be seen by the tuner or give no signal, make sure that you use the best antenna appropriate for the distance and frequencies being broadcast in your area. Point the antenna in the correct direction. See http://www.antennaweb.org or http://www.tvfool.com
for information on the stations near you. Antennaweb gives a very conservative list even though it assumes an external antenna.
I hope this helps.