you are unable to increase disk size on virtual machine ,Disk Provisioning option has grayed out even you have disk space on data store . this may be following cases you have migrated P2V , and your disk adapter type is IDE or Snapshot is associated with the virtual machine.
If you have space on data store and disk provisioning option has grayed out then check before doing anything your disk type ,in this image Disk controller type is IDE in this case you can not increase the disk size. you will have to convert your ddb.adaptorType = “ide” the the disk controller type to “lsilogic”
How to convert IDE to SCSI follow the link
How to Convert a virtual IDE disk to a virtual SCSI disk Step by step How to convert adapter stepbystep
SCSI disk option will give you to increase the disk size.
If your Disk is SCSI and Disk Provisioning option are grayed out.Then you are probably running off a snapshot.