Electrical tester says its hot but nothing is working
You are not using a "tester". You are using a voltage sensor. Big difference. 
You are getting a voltage reading but it's not working? This is almost certainly an open neutral on this circuit. A circuit needs both hot and neutral to work. 
Get yourself a real tester and test from hot to neutral and hot to ground anywhere possible.
Find the open neutral and you'll find your problem.

My real advice is to call an electrician. This would be the safest bet.