I have a Goodman GPM100-4 and the HSI does not glow. I smell has and inducer works fine. The board has a solid line (no blinking). I checked the voltage to the HSI and it is very low (5-10 Volts). Once the ignitor worked after not working for few days, but stopped working again. Thanks for your help.

That voltage is too low. It should be 120VAC. Start checking voltages elsewhere such as to the board, line and load of your transformer.