Please Guys I have been trying to install whatsapp plus on my infinix hot note lollipop but it always ends up with the 'app not installed' notification.. Any help/tip would be appreciated..

Conflicting Certificate.
The app you're trying to install was signed with a different key from the one in your device.
Since you say you're using an infinix, some Chinese phones preloaded some social media apps (eg WhatsApp, Facebook, etc) on their ROMs.
It's usually located in the root folder /vendor/app.
You can either delete it (you need superuser access) or disable signature verification in the package installer.
Either way your device needs to be rooted.

Chyjoey:
Please Guys I have been trying to install whatsapp plus on my infinix hot note lollipop but it always ends up with the 'app not installed' notification.. Any help/tip would be appreciated..

Hello, please check whether your phone has enough running storage and whether it has connected to Network normally first. If these are all ok, please change to download another version to have a try. If it still doesn't work, we suggest you take your phone to local Carlcare Service Center, the colleagues there will help you check it. If you need the contact information of the service center, please tell us the city and state you are living in now. Thank you!