ipod shuffle cable pinout and voltage

hi guys.

i have an ipod shuffle 4th gen

it was unused for a long time like 9 month or more

today i want to use it but it doesn't work at all. no turn on. no light. not even accept the charge

i tested it with laptop usb port and wall charger (iphone 6s charger). nothing happend.

so i opened it and check the battery voltage it was below 3Volts.

i charge it with lab power supply on 4.2Volts.

now ipod turns on and work fine. but the charge problem still here.

the computer doesn't recognize it connected.

so i check the cable with multimeter (volt meter)

i have 2.88Volts between pin 4 and pin 3

but the usb voltage is 5volts.

why this cable gives me 2.88Volts?

is there any pcb in usb socket?

or its just wire like micro usb cables?

thanks regard

(it was very very and very hard to open this tiny device)