Rick,

Gremlins. For sure.

OK, really. When you say it can't be relit, do you mean that it lights but won't stay lit or no gas to the pilot with the button depressed? Is this one of the new sealed burner type?

Normally, I would guess thermocouple if the pilot lights but does not stay lit.

How about a new installation and debris in the gas line to the pilot"

Possibly a faulty control valve assembly.

Does it sound like I am guessing? Yep. I'm going back to gremlins.

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The apostrophe troll.