look for the vdi name in the storage tab for the VM. then please try this.
xe vdi-list name-label
xe vbd-list vdi-uuid=&
then you need to unplug the vbd vai xe vbd-unplug
or simply , if the Storage is lvmoiscsi or lvmohba then then simply forget the vdi and re-attach the disk to the vm but please first ensure the sr scan is working fine,