Toshiba computer won't start up

My Toshiba laptop has a big issue. Even when I have the charger plugged in it won't charge. Sometimes when I leave it in my bag (charging port facing down) it will start back up when plugged in but when unplugged again it will stop. I don't know if this is a charging issue or a motherboard issue. Can you help me find out what to do and if I need it fixed by a third party where to get it fixed and the price (CDN). Thanks