Open System Preferences > Security & Privacy > General (tab)
Click the lock to unlock and then allow the system software from “PCLOUD LTD”. Restart your device.
Note:pCloud Drive requires the installation of a system extension in order to run smoothly. During installation, you will be required to enable the system extension from the Security & Privacy settings of your device. The system extension is not harmful - without it, pCloud Drive will not behave properly.