Shahedbro, u are facing same problem? please share us, if any methods work.
Many users have reported the same issue , that's actually the software bug after updating to 0.73 version and that's because the so called asus development team has messed up with firmware.
So the only solution to this problem is taking your device to authorised service centre.
Christine_ASUSnot working. its storage is dead, well done ASUS!
Please try following steps to access recovery mode.
1. Keep pressing "volume down key"
2. Press "power key" and stop press " power key" once you feel the vibration
3. Still keep pressing "volume down key" and stop press "volume down key" once you enter [Android Recovery] Screen
4. Choose "Wipe data/factory reset"
#Hardware Reset Guide
If the situation remain the same, please contact ASUS repair center in Bangladesh