rippled: After restart rippled, the server show InsufficientNetworkMode, why network not synced?

I have run rippled in testnet for 3 weeks with no problem , but after restart rippled today, it show InsufficientNetworkMode, I check that the peer is connected, and the rippled use half of memory. #2280

[ripple@Paci-RIPPLE-DEV build]$ /home/ripple/build/rippled --conf=/home/ripple/build/cfg/stg/rippled.cfg account_info rsK2DRGED8RDmPaeZW4MQHxkabEj9hji8u
Loading: "/home/ripple/build/cfg/stg/rippled.cfg"
2018-Jan-15 06:50:31 HTTPClient:NFO Connecting to 127.0.0.1:5005

{
   "result" : {
      "error" : "noNetwork",
      "error_code" : 17,
      "error_message" : "InsufficientNetworkMode",
      "request" : {
         "account" : "rsK2DRGED8RDmPaeZW4MQHxkabEj9hji8u",
         "command" : "account_info"
      },
      "status" : "error"
   }
}

[ripple@Paci-RIPPLE-DEV build]$ /home/ripple/build/rippled --conf=/home/ripple/build/cfg/stg/rippled.cfg server_info
Loading: "/home/ripple/build/cfg/stg/rippled.cfg"
2018-Jan-15 06:51:07 HTTPClient:NFO Connecting to 127.0.0.1:5005

{
   "result" : {
      "info" : {
         "build_version" : "0.90.0-b2",
         "closed_ledger" : {
            "age" : 7,
            "base_fee_xrp" : 1e-05,
            "hash" : "784D5895F73057B32C4AA0DEBA16F2563FBD1A45192EA283C3B34124BEB5E71C",
            "reserve_base_xrp" : 20,
            "reserve_inc_xrp" : 5,
            "seq" : 5857592
         },
         "complete_ledgers" : "empty",
         "fetch_pack" : 16,
         "hostid" : "Paci-RIPPLE-DEV",
         "io_latency_ms" : 1,
         "last_close" : {
            "converge_time_s" : 1.999,
            "proposers" : 0
         },
         "load" : {
            "job_types" : [
               {
                  "job_type" : "untrustedValidation",
                  "per_second" : 1
               },
               {
                  "job_type" : "untrustedProposal",
                  "per_second" : 31
               },
               {
                  "avg_time" : 6,
                  "job_type" : "ledgerData",
                  "peak_time" : 188,
                  "per_second" : 3
               },
               {
                  "in_progress" : 1,
                  "job_type" : "clientCommand"
               },
               {
                  "job_type" : "writeObjects",
                  "per_second" : 118
               },
               {
                  "job_type" : "peerCommand",
                  "per_second" : 342
               },
               {
                  "job_type" : "SyncReadNode",
                  "per_second" : 338
               },
               {
                  "job_type" : "AsyncReadNode",
                  "per_second" : 2464
               },
               {
                  "job_type" : "WriteNode",
                  "per_second" : 276
               }
            ],
            "threads" : 16
         },
         "load_factor" : 1,
         "peers" : 10,
         "pubkey_node" : "n9LnwURHfsUFdMVKCdzAnTcoo5gCamEdvjCNJvtUZWzKoKyp4HEr",
         "pubkey_validator" : "none",
         "published_ledger" : "none",
         "server_state" : "connected",
         "state_accounting" : {
            "connected" : {
               "duration_us" : "2165121769",
               "transitions" : 2
            },
            "disconnected" : {
               "duration_us" : "1497681",
               "transitions" : 1
            },
            "full" : {
               "duration_us" : "60023306",
               "transitions" : 1
            },
            "syncing" : {
               "duration_us" : "0",
               "transitions" : 0
            },
            "tracking" : {
               "duration_us" : "63",
               "transitions" : 1
            }
         },
         "uptime" : 2227,
         "validation_quorum" : 3,
         "validator_list_expires" : "never"
      },
      "status" : "success"
   }
}


Every 2.0s: /home/ripple/build/rippled --conf=/home/ripple/build/cfg/stg/rippled.cfg server_info | egrep 'load_|complete|peers|status...  Mon Jan 15 15:51:47 2018

Loading: "/home/ripple/build/cfg/stg/rippled.cfg"
2018-Jan-15 06:51:48 HTTPClient:NFO Connecting to 127.0.0.1:5005

         "complete_ledgers" : "empty",
         "load_factor" : 1,
         "peers" : 10,
         "server_state" : "connected",
         "uptime" : 2267,
         "status" : "success"