It won't heat up where. is the internal fuse if there is onr
It stopped heating up when I was in the middle of using it
It could be any number of things that caused this to happen.
A faulty cord, a faulty switch, a faulty heater element, a faulty thermistor etc.
The hair dryer would need to be opened and tested with a DMM (digital multimeter) to find out exactly what and where the problem is.
An appliance repair service could fix it but any reputable repairer would refuse on the basis that it would cost more in labour to find out what is wrong than what a new compatible hair dryer would cost.
If you have a DMM or know of someone who does then maybe you can fix it yourself or they can fix it for you.
Also if it is a faulty component e.g. a burnt out heater element, it may be difficult to source replacement parts as the manufacturer may not have any available due to it being manufactured as a “non- repairable” item as this is their business model i.e. no spare parts, but you may be lucky as it may be a common part over a lot of different brands