Foreman unable to find an unused IP

I'm using Foreman with Smart Proxy (MS Smart Proxy).

I've added the DHCP/DNS features to Foreman, and it seems to be ok.

I have for one subnet, one compute profile which is attached to this subnet.

I've tried to create a host manually via the Foreman UI, and attached it to
a pre created host group, which has been assigned to the subnet.

When i've tried to configure the NIC through the configuration screen and
get an IP ("Suggest new") i got the following error:

Failed to fetch a free IP from proxy uslabdns1.mydomain.com 

(https://uslabdns1.mydomain.com:8443): ERF12-8202
[ProxyAPI::ProxyException]: Unable to retrieve unused IP
([RestClient::ResourceNotFound]: 404 Resource Not Found) for proxy
https://uslabdns1.mydomain.com:8443/dhcp