Unable to copy the files to /system/app
Configuration to unmount the system,

adb shell

reboot bootloader

fastboot oem unlock


Reboot the devices,

adb root

adb disable-verity

adb root

adb reboot

adb root

adb remount

adb push adb push 'D:\VINOTH'   /system/app/


Wait until finish

adb reboot