have a macbook air with issues. tried to reset OS and now when i power up all i get is flashing ? on a folder? please help!!!

[JTIZZLE]

got a used macbook air for my sister. it has some power issues. Tried to reset the os at best buy. and it worked till i got home. Now when i power it up all i get is a blank screen with a flashing ? on a folder. Please help.

 

[nolimits76]

https/support.apple.com/en-us/HT204323