A leak coming from the vent or duct above your microwave could be due to several issues. Since it’s on the first floor, it’s unlikely to be a roof leak. More commonly, it could be condensation from your HVAC system, especially if the ductwork is not insulated properly or if there's a blockage causing moisture to accumulate. Another possibility is a plumbing issue, such as a leak from nearby pipes or even a malfunctioning appliance.
Given that the leak is affecting your microwave, it’s essential to address this promptly to prevent further damage or potential electrical hazards. I recommend checking the ductwork for any visible signs of moisture and ensuring that your HVAC system is functioning correctly.
However, for safety reasons, especially with electrical and plumbing components involved, it's best to consult a licensed professional. They can accurately diagnose the source of the leak and make necessary repairs. Typically, you can expect to pay between $75 to $150 per hour for a licensed HVAC or plumbing technician, depending on your location.
As a next step, get 2-3 local quotes on Handyman.com to find a professional who can assess and resolve the issue.
— Assisted answer