privileged API user cannot edit CoGroup in CO

cat << EOF > co_groups.json
{
"RequestType":"CoGroups",
"Version":"1.0",
"CoGroups":
[

{ "Version":"1.0", "CoId":"2", "Name":"Test Group 01", "Description":"Edited by REST API", "Open":false, "Status":"Active" }

]
}
EOF

curl \
-k \
--verbose \
-u 'co_2.rest_user_01:XXXXXXXX' \
-X PUT \
-H 'Content-Type: application/json' \
-d @co_groups.json \
'https://registry-dev.skoranda.scgvm.net/registry/co_groups/31.json' | jq

Fails with a 401