no problem with 17.04 or earlier nfs on 17.10 does not work with no changes between upgrade.

the error / problem:

mount.nfs: access denied by server while mounting xx.xx.xx.xx:/var/www

my nfs install routine:
server: (fresh 17.10 install)

sudo apt-get update
sudo apt-get install nfs-kernel-server --yes
sudo mkdir -p /var/www
sudo nano /etc/exports
    /var/www yy.yy.yy.yy(rw,sync,no_root_squash,no_subtree_check)

sudo exportfs -a
sudo service nfs-kernel-server restart

client: 17.10

sudo mkdir -p /mnt/nfs/test
sudo mkdir -p /mnt/nfs/test/www
sudo mount xx.xx.xx.xx:/var/www /mnt/nfs/test/www

sudo nano /etc/fstab
    xx.xx.xx.xx:/var/www /mnt/nfs/test/www/ nfs auto,noatime,nolock,bg,nfsvers=4,intr,tcp,actimeo=1800 0 0
this exact process works for 17.04, but not 17.10 

any help appreciated.