Tripped GFCI

I have an outdoor GFCI outlet right by the patio door wall that connects downstream to a regular outlet in the Gazebo. Many times after heavy rain the Gazebo outlet would not work cause the GFCI outlet would trip. So I would reset it. Happened probably 5 or 6 times over a year. Lat year after being tripped again the GFCI outlet won't reset anymore, tried numerous times and tries again yesterday. I figured it needs to be replaced but I can't find a circuit breaker int he house that the GFCI outlet is connected to and so I can't turn off the electricity to it to change it. I have used a current detector and it indicated current is running to the GFCI but as expected no current in the Gazebo outlet. Any advised or help would be appreciated. Thank you.