Control by default uses IpNetToMedia, IpNetToPhysical, CtAlias to actively discover IP addresses. In this case because Control cannot establish SNMP contact we don't know what worker to use for IP resolution, so likely we won't even try.
You can take a tcpdump on control, it's unlikely that the HP switches are responding, maybe they need to be configured with NAC as an SNMP server?
By default Control will NOT use DHCP requests for IP resolution. They are not trusted by default. If you go into Engine Settings --> IP resolution and set "Use DHCP Request IPs" to "Always".
This will have Control use the request IP's discovered as a last resort.
Even if you got contact to these switches with SNMP it's unlikely IP resolution would be any better as they are HP and don't support CtAlias.