What could be wrong with your home AC central air if the thermostat clicks on and fan but AC unit won't start and new fuses and switching the breaker on and off didn't help?

It could be off on a low pressure switch. You need to check if you have 24 volts to the outdoor unit at the contactor coil. If the contactor is not working the outdoor unit will get no high voltage to the compressor or fan. It could also be that the capacitor for the fan and compressor is blown.