If voltage at gfci, line side, is zero, then you have a problem between the breaker and the gfci. If voltage is good at line side, then your problem is at gfci, or down the line.
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It sounds like you should be under supervision allot. You don't use a proximity tester to check for voltage. Find a good co-worker and ask, you'll be surprise, allot of people are willing to help.
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