dear, I'm with error version 4.3 does not start. please.

 traccar.service - traccar
   Loaded: loaded (/etc/systemd/system/traccar.service; enabled; vendor preset: enabled)
   Active: failed (Result: exit-code) since Wed 2019-02-27 08:02:48 EST; 11s ago
  Process: 2400 ExecStart=/opt/traccar/jre/bin/java -jar tracker-server.jar conf/traccar.xml (code=exited, status=1/FAILURE)
 Main PID: 2400 (code=exited, status=1/FAILURE)

Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3914)
Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:871)
Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.MysqlIO.proceedHandshakeWithPluggableAuthentication(MysqlIO.java:1714)
Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.MysqlIO.doHandshake(MysqlIO.java:1224)
Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.ConnectionImpl.coreConnect(ConnectionImpl.java:2199)
Feb 27 08:02:48 vps225958 traccar[2400]:         at com.mysql.jdbc.ConnectionImpl.connectWithRetries(ConnectionImpl.java:2046)
Feb 27 08:02:48 vps225958 traccar[2400]:         ... 22 more
Feb 27 08:02:48 vps225958 systemd[1]: traccar.service: Main process exited, code=exited, status=1/FAILURE
Feb 27 08:02:48 vps225958 systemd[1]: traccar.service: Unit entered failed state.
Feb 27 08:02:48 vps225958 systemd[1]: traccar.service: Failed with result 'exit-code'.

logs

2019-02-27 07:40:38  INFO: [04e0ccf6: 5055 < 127.0.0.1] HEX: 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
2019-02-27 07:40:38  WARN: Unknown device - 851119 (127.0.0.1)
2019-02-27 07:40:38  INFO: [04e0ccf6: 5055 > 127.0.0.1] HEX: 485454502f312e31203430302042616420526571756573740d0a636f6e74656e742d6c656e6774683a20300d0a0d0a
2019-02-27 07:40:38  INFO: [7849f1a1: 5055 < 127.0.0.1] HEX: 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
2019-02-27 07:40:38  INFO: [7849f1a1: 5055 > 127.0.0.1] HEX: 485454502f312e3120323030204f4b0d0a636f6e74656e742d6c656e6774683a20300d0a0d0a
2019-02-27 07:40:51  INFO: Shutting down server...
2019-02-27 07:42:46  INFO: HikariPool-1 - Starting...
2019-02-27 07:42:51 ERROR: HikariPool-1 - Exception during pool initialization. - Could not create connection to database server. Attempted reconnect 3 times. Giving up. - MySQLNonTransientConnectionException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)
2019-02-27 07:42:51 ERROR: Main method error - Failed to initialize pool: Could not create connection to database server. Attempted reconnect 3 times. Giving up. - PoolInitializationException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)
2019-02-27 07:46:10  INFO: HikariPool-1 - Starting...
2019-02-27 07:46:15 ERROR: HikariPool-1 - Exception during pool initialization. - Could not create connection to database server. Attempted reconnect 3 times. Giving up. - MySQLNonTransientConnectionException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)
2019-02-27 07:46:15 ERROR: Main method error - Failed to initialize pool: Could not create connection to database server. Attempted reconnect 3 times. Giving up. - PoolInitializationException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)
2019-02-27 07:49:32  INFO: HikariPool-1 - Starting...
2019-02-27 07:49:36 ERROR: HikariPool-1 - Exception during pool initialization. - Could not create connection to database server. Attempted reconnect 3 times. Giving up. - MySQLNonTransientConnectionException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)
2019-02-27 07:49:36 ERROR: Main method error - Failed to initialize pool: Could not create connection to database server. Attempted reconnect 3 times. Giving up. - PoolInitializationException (... < DataManager:139 < *:89 < Context:389 < Main:110 < ...)

Error messages are pretty self-explanatory. Server is not able to connect to your MySQL database.

grato