Why is my Flash not fire

Hi

Camera Nikon D5600

When in auto mode flash pops up but flash is not firing and shutter can't be reliesed. All settings have been tested. Warranty has just gone out so I have to fix it myself. Could it be mecanism faliur or bad connection, broken flash bulb or pcb board faliur. How can I test it. Is it possible to fix it myself or should I leave it to proffesionals maybe it's more cost effective to buy a new camera.

Sincerely

Jan-Olof Björdal