Can't use unallocated space on a Win 2k8 R2 VM

I'm hoping someone can help me with this because after 2 days of googling I've come up with nothing.

I have a file server that I have converted from a physical to a virtual on an ESXi 6 host. I have increased the disk size in ESXi by 400GB's, and in windows I can see the unallocated space, however when i try to extend a partition or create a new one I receive the error:

"There is not enough space available on the disk(s) to complete this operation"

Initially the disk was basic so I converted it to dynamic thinking this could be the problem (even though I've increased basic disks before), and I still got the same error message.

I read that this issue is sometimes caused by there not being enough space at the end of the disk, and shrinking the volume by 100MB can resolve it, I did this and another section of unallocated space appeared in disk manager, in which I can create a new volume of 100MBs or extend the partition back by 100MB.

For some reason, the unallocated 400GB is completely unusable and I don't know why.

Screenshot of Disk Management and error message:

Screenshot of partitions in DISKPART:

Any help would be greatly appreciated.

P.S I have tried a rescan as 90% of webpages told me to do, to no avail.