Comment 1 for bug 1969592

Nova compute waited for 300 sec to get a network-vif-plugged event then timed out:

2022-04-19 12:35:11.842 8 ERROR nova.compute.manager [instance: 7560fbb7-3ec7-41ef-b7a5-5e955ca4ff34] eventlet.timeout.Timeout: 300 seconds

Do you have a bit more logs from the nova-compute service? If you have debug log enabled then from the nova compute logs we can puzzle together what for what ports nova got the plugged event and for what port such event was missing.

I'm not sure but this might mean that neutron never sent the plugged event as the port was down in the OVN backend:
2022-04-19 12:35:11.330 25 INFO neutron.plugins.ml2.drivers.ovn.mech_driver.mech_driver [req-2b4d10b1-3a7a-4683-97df-990259705b46 - - - - -] OVN reports status down for port: be178a9a-26d7-4bf0-a4e8-d206a6965205

Somebody with neutron + OVN knowledge should look at this.