I have a 2002 LP Hi-Eff coleman furnace. I've been getting the 7 red blinking lights which is ignition lockout. I have removed the flame sensor and cleaned it with steel wool and it worked a few more times in a row and then locksout. (it doesn't do it every time seems random) Today I bought a new flame sensor and installed it and having the same issues. What else can cause the ignition lockout error?

Watch the ignition sequence & tell us, in detail, what happens.