Openstack instance create error: Failed to allocate the network(s) with error No fixed IP addresses available for network

The log shows that sending hdr requests to tgt failed, so there is a problem with the tgtd service [tgtd iSCSI target daemon]. The tgtd iSCSI target daemon means that tgtd is the background service of the iSCSI target, that is, the daemon. Execute the command systemctl status tgtd and find that the service is in the disabled state.
So start the service systemctl start tgtd can solve the problem