When LUNs are newly mapped to a host, the host often needs to be rebooted to bring all OVN paths to the LUNs online at the host.
No reliable workaround is known. Steps such as setting the vHBAs down and then up or rescanning the vHBAs at the Oracle Fabric Interconnect followed by running cfgadm on the host will sometimes bring all paths online, but often only bring some of the paths online.