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Does the burner fire up then lock out or not fire and lock out?
Sounds like your burner needs a tune up if it doesn't fire up when it should. If it locks out when it is firing then you could have a bad/dirty cad cell (electric eye) or cad cell socket since this would indicate the control isn't seeing the fire
Just turn off the power and release the 2 screws at the front of the burner transformer. Then swing the transformer back on its hinge. The cad cell is under the transformer. It's plugged into a socket that has 2 yellow wires. Make sure the glass end is clean. That's they only easy thing you can do.