Neutron crash on overcloud and did not recover

Issue

• When logging into Horizon, we are unable to retrieve network or instance lists.
• pcs status shows most of the resources for Nova, Neutron, & Rabbit in a failed/unmanaged state.
• Restarting the resources fixed the issue, but why did they not recover automatically?
• Cluster did not recover automatically after quorum was lost, and then regained. Manual intervention was required.