Hi
axisrmThank you for your asking. Because your firmware is the latest version, please try the following steps to access recovery mode for the Factory Reset:
0. Try to back up your data with USB cable. If you can not access the phone, please check if your google account or microSD card have auto backup your data.
1. Power off the phone, then keep pressing "volume down key"
2. Press "power key" and stop press " power key" once you feel the vibration. Still keep pressing "volume down key".
3. Stop press "volume down key" once you enter [Android Recovery] Screen
4. Choose "Wipe data/factory reset">"Yes"
5. "Reboot system now"
#Hardware Reset Guide
https://www.asus.com/support/FAQ/1006346/Please note that once the steps are completed, all data, apps, settings and personal information will be deleted.
If the situation remains the same, kindly provide the information below so that we can better assist you.
1. Does the issue appear right after any system/apps' download or update?
2. Which app do you try to install? Does the issue occur while installing all the apps, installed app or third party app?
3. If you do not insert the SD card after performed the Factory Reset, can you install the apps?