Lightroom does not use plugins (Adobe Camera Raw) to read Raw files. It has its own Raw engine built in.
Camera Raw plug-in | Supported cameras
The Nikon D810 was first supported in Lightroom 5.6.
Support for newer cameras is never added retrospectively to older versions of the software so you'll never be able to open Raw D810 files in LR 4.4.
Choices:
- Upgrade to Lightroom 5, or
- Download the free Adobe DNG converter, convert all D810 Raw files to DNG format then edit the DNGs in LR 4.4
Digital Negative (DNG)