Mounting an NFS share on a client machine fails

Hi everyone,
I am looking for some help here in mounting a NFS share I have on my OpenMediaVault server with tailscale installed and working as an exit node and with subnets routed.

On my client machine, running Debian 11, if I connect to Tailscale with sudo tailscale up --exit-node=100.105.xx.xx --exit-node-allow-lan-access=true --accept-routes

and try mounting the share with; sudo mount -t nfs 100.105.xx.xx:/data /mnt/data/
it returns the following error
mount.nfs: access denied by server while mounting 100.105.xx.xx:/data

Turning off the client side Tailscale connection and the NFS share is mounted as expected.
I am a relative noob and would greatly appreciate in help/advice in solving this.