Unable to access file [datastore_name] VM_name

I have an NFS storage system based on Windows Server 2012 R2.

I create a volume (520GB) with appropriate permissions and settings.

Then I attach it as datastore to my ESXi host (ESXi 5.5.0, 2068190).

I attach it without any problem but when I try to attach a disk to any VM on this ESXi from this datastore I get error "Unable to access file [datastore_name] VM_name"

what can be the issue?

already applied these but with no luck

Unable to read / write to NFS datastore

Business Storage Windows Server NAS - How to create a VMware NFS datastore

Re: Can't add an NFS share on my ESX host.

http://www.vmware.com/files/pdf/techpaper/VMware-NFS-Best-Practices-WP-EN-New.pdf

unable to write to NFS datastore

Unable to create VM in NFS Based Datastore.