Looking at the screenshot looks like you have 2 virtual disk on same disk group. You can not expand the virtual disk size if there are more than one virtual disk on the same disk group. One option I can recommend is
Hi all, I have a Power Edge server T320 with controller Perc H310 with 5 disks in raid 5. I decided to change the whole set of disks (5x1TB) with 5 2TB Wd Gold. I replaced the disks one by one, the raid was successfully rebuilded with no problems, but I have a problem, the whole capacity of the virtual disk remained 3,7 TB, on OMSA I don't have any option to expand the capacity, neither from bios. Into the bios the option Expand Capacity is grayed out. In OMSA every single disk property is  How can I expand the capacity so I can use all the available space of the new set? I need also to change the size of the 2 virtual disks into the raid, one is 100 GB for OS Windows server going out of space) and the other is 3,6 TB used for sharing files.  Thank you in advantage for any help.
T320 Perc H310 Raid 5 Replace disk with size upgrade