Why is my phone ignoring OTG USB? I have 2 phones.
 1. Android 4.4.4 - When OTG USB is connected, it automatically mounts with no problems and I can manage files, watch movies from it, etc.
 2. Android 6.0 - when OTG USB is connected, phone fully ignores it (does nothing).

Why can't second phone mount it exactly like a first does? Do I have to install some application that takes care of it? First phone is rooted, second is not. Can that be a problem?
Its not the android version describes that it can connect OTG(On-The-Go), its the capability of the device. Huawei P8 Lite has no OTG connectivity as described here : P8 lite review