My thermostat is on but it is taking too long for the floor to warm up/not heating up at all.
Check to make sure that you have wired the thermostat correctly, following the instructions detailed in the basic installation instructions.
If the wiring is correct, use a multi-meter and take readings from your heating system wire (See installation manual for your heating system).
Did you install WIB (Warmup Insulation Board) over your concrete slab? If not, it will take longer for your floor to reach the target temperature.