Run the dryer and check for voltage to the burner assembly. If you have voltage (120v) and the ignitor doesn't glow, you need to check resistance, not continuity. Most ignitors are under 100 ohms, anything higher it should be replaced. If the ignitor ohms out ok, Then the only thing left is the flame sensor...you can also ohm out (or check continuity) the flame sensor, which should be less than one ohm, or it should have continuity.
The flame sensor allows voltage to reach the ignitor, once the flame heats the bi metal up in the flame sensor, its contacts separate and the ignitor no longer gets voltage.
If you arent getting voltage to the burner assy, there is multiple fuses to be checked. all should have continuity when cold....Then one with 4 wires should only have continuity in one direction but not both (purple to purple or red to red if i'm right about the colors)