I Had SF cluster made of 3 Standard A0 nodes. I scaled cluster in to 1 node and understood that this was bad idea because nothing was working in this state (even SF explorer was not working) Then I scaled it out back to 3 nodes and restarted Primary scaleser. Now all nodes in scaleset are up and running but SF cluster status is "Upgrade service unreachable". I saw similar question Service Fabric Status: Upgrade service unreachable where was recommended to scale nodes up to D2 but this hasn't solve my problem. I have connected to one node via RDP and are some Event logs:
EventLog -> Applications and Service Logs -> Microsoft Service Fabric -> Operational:
Node name: _SSService_0 has failed to open with upgrade domain: 0, fault domain: fd:/0, address: 10.0.0.4, hostname: SSService000000, isSeedNode: true, versionInstance: 5.6.210.9494:3, id: d9e8bae2d4d8116bfefb989b95e91f7b, dca instance: 131405546580494698, error: FABRIC_E_TIMEOUT
EventLog -> Applications and Service Logs -> Microsoft Service Fabric -> Admin:
client-10.0.0.4:19000/10.0.0.4:19000: error = 2147943625, failureCount=487. Filter by (type~Transport.St && ~"(?i)10.0.0.4:19000") to get listener lifecycle. Connect failure is expected if listener was never started, or listener/its process was stopped before/during connecting.