I recently changed the IP Address of a QNAP TS-231 NAS Appliance that I was using to mount .ISO files to virtual machines. I disconnected all virtual machines from the datastore (SharedISO) and then successfully deleted the datastore in the vSphere WebUI. When I attempted to re-add it using the new IP Address I received the following error:
To fix the problem I opened an SSH session to my ESXi host and executed the following command.
esxcfg-nas -d SharedISO