Heating not turning on
I see a spare fuse in there it could be a sign it blows fuses
also check at the heat elements there is a mechanical thermal safety for over temp. Most electrics have a breaker panel on the unit itself.
I can not tell the breaker values feeding the unit if there are multiple breakers it is is back to the controls again back to the fuse or thermal limit.
I only see 1 element with the yellow blue wires the blue wire is connected to the thermal limit tap that black thing and yes there could be power right there.
So a control fuse is open or the limit, if the thermostat is sending the call for heat those art the 2 prime suspects.
If you have a volt meter and know how to use we may offer more help