Disk 1 has two volumes (2048 GB NTFS and 743.87 GB Unallocated). First volume can’t be extended (grayed out) because Disk 1 was created with MBR disk.
To extend beyond 2 TB capacity, you need to convert Disk 1 to GPT disk, (GUID Partition Table).
- Make a full backup of Drive-D (Data).
- Delete data (D:) volume.
- Create new volume (GPT Disk).