First of all  would recommend to take a immediate backup as you had one drive failed and one drive came to foreign state.  From screenshot it looks like you have SATA HDD drive on existing virtual disk and new drive installed is SATA SSD. We can not mix HDD and SSD on same virtual disk. That is the reason you are not able to assign new drive to the virtual disk. Which server did you have?
I am working on restoring a RAID 5 setup after a bad shutdown from power loss. The full RAID uses 3 disks, each 250GB.   Summary: After the outage, one disk was seen as foreign and one disk had failed. I was able to load the foreign config and restore server functionality.  We purchased a replacement disk of the same capacity and swapped out the old disk for the new one. It appears with the ready status and can be assigned as a Global Hot Spare - but when doing so I get the following message: "WARNING! None of the existing VD's will be covered by this Hot Spare.  (ERROR Code: 0xc)" I need to figure out a way to get the RAID 5 healthy again. I have attached images for further information. Nothing I've tried has been able to get this running again. I am unable to add a disk to the VD or the existing disk group.  [IMAGE][IMAGE][IMAGE][IMAGE][IMAGE][IMAGE]
Dell PERC 6/i | RAID 5, unable to replace a bad drive