Took me all day to figure this out. Xen 7.3 does not come with NFS support oddly. So you need to install it.
First you will surely need the epel repository
yum --enablerepo=extras install epel-release
Now you can install other packages.
yum --enablerepo=epel --enablerepo=base install nfs-utils
I also like MC so let’s install that too.
yum --enablerepo=epel --enablerepo=base install mc
Some useful commends to test NFS.
rpcinfo -s <IP>
showmount -e <IP>