Cannot mount ZFS pool on remote host

I have (for testing purposes using a USB-attached drive) setup a ZFS pool that I would like to share via NFS to one client.

Note that I pretty much followed the information from this post which is not working as suggested: https://www.hiroom2.com/2016/05/18/ubuntu-16-04-share-zfs-storage-via-nfs-smb/

Note that I am new to this on Linux so may be asking some schoolboy questions and I am new to posting here so learning all of the this formatting as I go!

ZFS host is Ubuntu 20.04. and the client is also Ubuntu Desktop 20.04.

On the ZFS host I have created the pool called:

usb-WD_Elements_25A3_33574A394C31574A-0:0_pool

This pool is mounted locally on the ZFS host as:

/mnt/zfs/testusb/

I can use the mountpoint and have tested exporting the pool and importing on another PC and it works well.

Now I want to share this pool from one host to a client using NFS so I enabled ZFS's sharenfs by using:

zfs set sharenfs="[email protected]/24" usb-WD_Elements_25A3_33574A394C31574A-0:0_pool

&

zfs get sharenfs | grep usb

shows me:

usb-WD_Elements_25A3_33574A394C31574A-0:0_pool   sharenfs  [email protected]/24  local

df -k | grep usb outputs:

usb-WD_Elements_25A3_33574A394C31574A-0:0_pool     16T  5.2T   11T  33% /mnt/zfs/testusb/

zfs list | grep usb outputs:

usb-WD_Elements_25A3_33574A394C31574A-0:0_pool    5.15T  10.7T     5.15T  /mnt/zfs/testusb/

All good!!

I now go to the client PC (logged in as sudo -s) and run:

mount 176.1.1.2:usb-WD_Elements_25A3_33574A394C31574A-0:0_pool /mnt/zfs/testusb/

And I get:

mount.nfs: access denied by server while mounting 176.1.1.2:usb-WD_Elements_25A3_33574A394C31574A-0:0_pool

I'm clearly missing something but as this is my first time sharing a ZFS filesystem I am not sure what I've done wrong.

Thanks in advance!