Host virtual Flash resource cannot configure one or more SSD disks.
SSD disk attached to the virtual flash resource could have hardware issues or may be incompatible for use with vFlash.
Make sure that selected SSD is healthy and is not participating in any other vSphere activity
Check vSphere Storage documentation for more information on configuring vFlash resource for the host.
Refer to the VMware Online Documentation for more information on vCenter event messages and possible solutions.