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There probably is air in the line feeding the heaters and need to be bleed out or reset a few of times to get the air out by itself.
The furnaces should have LED lights blinking giving a fault code. Count the blinks.
Turn the furnace off at the switch and watch for normal sequence,draft inducer starts, ingnitor glows, gas valve open. You may hear the gas or air flow. If the ingnitor glows but no ignition try it once or twice more and see what happens.
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