Unable to mount an NFS share

I'm trying to access my (Synology) NAS share through NFS and always get the same issue.

First, I activated NFS support in my NAS:

Then I set the permissions on the NAS:

My MBP has the IP 192.168.1.109. From there it seems OK. a showmount -e 192.168.1.2 shows the list:
Exports list on 192.168.1.2:
/volume1/video 192.168.1.109
/volume1/homes 192.168.1.109

But unfortunately, my mount always fails: GroundControl:/ ludo$ sudo mount -t nfs -o rw 192.168.1.2:/volume1/homes /Volumes/home
mount_nfs: can't mount /volume1/homes from 192.168.1.2 onto /Volumes/home: Operation not permitted

The /Volume/home directory is created upfront.

Trying with a non-existing share on the NAS, for example /volume1/qwerty gives a Permission denied error, which is OK.
But what is this Operation not permitted error?

Trying through DiskUtils>NFS Mounts gives the same result.

What did I miss?

Or just use the "resvport" option with the mount command.

mount -o resvport nasbox.local.com:/try /mnt

Finally found the solution in an old forum thread.

My solution was to mount with "-P" to force the use of a reserved port number, as described in mount_nfs(8) page.

The solution is then to use the -P option to the mount command.
Now works like a charm (but doesn't fix my initial issue!)