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Hello, this might be an Olsen brand but made by Newmac look this link over briefly please and tell me if this is what you have, or if it is close
Tell me if the exhaust blower is running or not, and if there is a flue damper on the vent pipe and if it is open or not.
That is the most likely point of failure, a failed inducer fan or stuck vent damper.
Next send me a photo of the wiring diagram glued inside the electrical control panel, use the paper clip icon at the right end of your tool bar for that, or the 'attach files' link to the left of your send button.
Photo must be well focused, in good light, taken up close, and from straight on.
We can go from there.