I have re the above post as they had the exact same issue I am getting. They seem to have resolved it but I can't see a solution that I can replicate.
I am also trying to mount a NFS share (from FreeNas) as a remote within XO. It throws back the same error as in the above post. I also can't add NFS direct into XCPNG centre as an SR with fail to find NFS errors being returned. I have confirmed the NFS share is visible elsewhere.
Am very confused what issue would be stopping this so any help would be much appreciated.