@fabrice my data/config.json contains
{
“Archival”: true,
“isIndexerActive”: true,
“GossipFanout”: 4,
“BaseLoggerDebugLevel”: 1,
“IncomingConnectionsLimit”: -1,
“NetAddress”: “0.0.0.0:4160”,
“EndpointAddress”: “0.0.0.0:8887”,
“LogSizeLimit”: 1073741824,
“EnableMetricReporting”: false,
“EnableOutgoingNetworkMessageFiltering”: true,
“EnableIncomingMessageFilter”: false,
“CatchupParallelBlocks”: 50
}
i have set up the nodes in 2 servers and after upgrading the node to 2.5.5 in both the servers it has started syncing in one and not in another
The server where is is syncing the latest block is 156000
when i do curl to get latest block in server not syncing i get the below
{“lastRound”:13409875,“lastConsensusVersion”:“https://github.com/algorandfoundation/specs/tree/3a83c4c743f8b17adfd73944b4319c25722a6782",“nextConsensusVersion”:“https://github.com/algorandfoundation/specs/tree/ac2255d586c4474d4ebcf3809acccb59b7ef34ff”,“nextConsensusVersionRound”:13409876,“nextConsensusVersionSupported”:true,“timeSinceLastRound”:0,“catchupTime”:0,“hasSyncedSinceStartup”:false,"stoppedAtUnsupportedRound”:false}
Below are the logs from node.log from Server not syncing 
{“Context”:“Agreement”,“Hash”:"",“ObjectPeriod”:0,“ObjectRound”:0,“ObjectStep”:0,“Period”:0,“Round”:12408305,“Sender”:"",“Step”:13,“Type”:“StepTimeout”,“Weight”:0,“WeightTotal”:0,“file”:“trace.go”,“function”:“github.com/algorand/go-algorand/agreement.(*tracer).logFastTimeout”,“level”:“info”,“line”:204,“msg”:“timeout fired on (12408305, 0, 13) with value 1h13m41.202589056s (napping: false)”,“time”:“2021-03-04T11:23:49.131181Z”}
{“Context”:“Agreement”,“Hash”:“AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA”,“ObjectPeriod”:0,“ObjectRound”:0,“ObjectStep”:0,“Period”:0,“Round”:12408305,“Sender”:"",“Step”:255,“Type”:“VoteAttest”,“Weight”:0,“WeightTotal”:0,“file”:“actions.go”,“function”:“github.com/algorand/go-algorand/agreement.pseudonodeAction.do",“level”:“info”,“line”:372,“msg”:"attested to {{} 0 AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAY5HFKQ AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA} at (12408305, 0, 255)”,“time”:“2021-03-04T11:23:49.131461Z”}
{“file”:“bootstrap.go”,“function”:“github.com/algorand/go-algorand/tools/network.ReadFromSRV",“level”:“info”,“line”:43,“msg”:"ReadFromBootstrap: DNS LookupSRV failed when using system resolver: no signature in DNS response for _algobootstrap._tcp.mainnet.algorand.network”,“time”:“2021-03-04T11:24:17.714479Z”}
{“file”:“wsNetwork.go”,“function”:“github.com/algorand/go-algorand/network.(*WebsocketNetwork).meshThread”,“level”:“info”,“line”:1341,“msg”:“got no DNS addrs for network mainnet”,“name”:"",“time”:“2021-03-04T11:24:23.716010Z”}
{“file”:“bootstrap.go”,“function”:“github.com/algorand/go-algorand/tools/network.ReadFromSRV",“level”:“info”,“line”:43,“msg”:"ReadFromBootstrap: DNS LookupSRV failed when using system resolver: no answer for (_algobootstrap._tcp.mainnet.algorand.network., 33) from DNS servers [127.0.0.11:53]”,“time”:“2021-03-04T11:25:18.551284Z”}
{“file”:“wsNetwork.go”,“function”:“github.com/algorand/go-algorand/network.(*WebsocketNetwork).meshThread”,“level”:“info”,“line”:1341,“msg”:“got no DNS addrs for network mainnet”,“name”:"",“time”:“2021-03-04T11:25:24.552928Z”}
{“instanceName”:“EwdHZyOJZ6fphxs2”,“level”:“info”,“msg”:"/ApplicationState/Shutdown",“session”:"",“time”:“2021-03-04T11:25:46.548776Z”}