If the battery is completely flat it can take a few hours before charging starts.
If it definately wont charge after say an overnight charge then it will most likely be the battery.
Most are replaceable but you may need a set of very small Torx drivers and good hand/eye coordination......they are fiddly to dismantle and the PCB to screen data ribbon connectors are extremely delicate and easily broken.....once broken you may as well bin it, dont ask how i know
you will find video instructions on the internet for dismantling.
Its also possible you may do the work for nothing.....my last one simply quit when in use.
Turned itself off, then back on, the off for good.
I just went and bought a new one.