The outlets on the master room bathroom and the bathroom on the 2nd floor has no pwr. This was verified with the use of a light indicator probes by checking the power on the outlets screws. The breakers were checked the same way, however there is power going to the breakers. One outlet that has the test/reset push buttons in the guest bathroom checked okay. There is one light switch in the bathroom upstairs that turn on/off a extractor fan that does not work, however there is power on the wires. I replaced the switch anyway. Nevertheless, Does the defective extractor would creates a open circuit. Please advise.

The fan itself wouln't create a problem within a circuit... it either works or does not. You have power to the GFCI, but does this outlet work? You can have power on the wires without having a complete circuit... that is an open neutral situation. Inspection is probably the only way you will find this issue. Remove every cover and check the wiring for power. Then turn off the power to to the switch, receptacle and pull it out and physically look for a loose wire or one that is burned or disconnected. Troubleshooting is the most difficult part in finding the problem. Good luck.