Custom ROM and rooted phones aren't supported by WhatsApp. There are too many variations in these customizations for us to maintain a working product. Furthermore, custom ROM and rooting do not allow the WhatsApp security model to function as intended. If you are using custom ROM or a rooted phone, your messages will not be protected with end-to-end encryption.
For the best WhatsApp experience, please use stock ROM and remove root. Please contact your phone's manufacturer for specific instructions on how to unroot.