Was there any recent change in DHCP client behavior? It used to send DHCPREQUEST as broadcast (rebind) when using “/ip dhcp-client renew” but is now sending unicast (renew) to DHCP server and does not time out (silently ignores situation where no response is received and does not fall back to rebinding). It is hence impossible to force rebind action on DHCP client without disabling and reenabling it. Additionally there is no “Renewing…” message even if server does not reply - so no indication whether action is being taken or not.