I just installed a new 20 amp GFCI in an outdoor outlet. There are only three wires coming out of the junction box, the black, white and copper wire. After installation, I turned the current back on to ensure the outlet was functioning correctly. It was. I wrapped the GFCI in electrical tape to cover the terminals. I then inserted the outlet into the junction box and it stopped working. Additionally I tested to see if there is no voltage in the neutral wire or the metal junction box. There is none. The wires coming out of the junction box do not have any obvious defects. The GFCI does not trip, it just receives no current after installation into the junction box. The only other device on the same circuit breaker is getting current and operates fine. Any suggestions would be appreciated.