Hi you can log thru SSH to the ESxi host i which the VM is residing.
then run the below command :
#vim-cmd vimsvc\task_list
this will show all the process running on the host,
please locate the snapshot process in this list
once you have the copy from "ha ...processid"
then run.
#vim-cmd vimsvc\task_info "ha ...processid"
here you will see "progress" - this will show if the process is running or not
if you do not see any process the snapshot is gone zombie - so you can kill it with the below command.
#vim-cmd vimsvc\task_cancel "ha ...processid"
later run
/etc/init.d/hostd restart
/etc/init.d/vpxa restart