I plugged my GFCI Outlet Tester into a GFCI protected Outlet. Pressing the test button, the outlet was tripped fine. But no matter how I pressed the reset button on the GFCI receptacle. The outlet showed no power. Could someone tell me why I cannot get power anymore from the outlet? Thank you.
Never mind. I thought the GFCI switch in the master bathroom was controlling the outlets in the same room. After some testings, however, I found out that the outlets were actually controlled by a GFCI switch in the guest bathroom. All the devices are working fine. Thank you all for your suggestions. Very much appreciated.
Replace the GFCI, it's shot
Given that it's a modern GFCI that did this, it's trying to tell you "I'm broken inside and can no longer provide GFCI protection" when it's stubbornly refusing to reset. So, it's time to replace it with a new GFCI; if you need help with that, post a new question here with photos of the inside of the junction box in question.