It needs to vent out to the exterior. Not to a soffit vent, or gable end vent or an attic vent. It needs it's own vent throught he roof.
I would have a professional roofer do this, you do not want a roof leak.
It may be why they did not vent it correctly in the first place, in fact it may not even be included in the price of the vent installation.
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