Mondrian Error:Internal error: Error while creating SQL connection (SQL Server)

I'm evaluation your Pivot Table Component for connecting to Mondrian/SQL Server. I have configured it to connect to Mondrian server via XMLA and everything it's working perfectly.
I facing problems with the Flexmonster accelerator. I can start it with no errors, but when I access the WebPage I get the following error:
SEVERE: Mondrian Error:Internal error: Error while creating SQL connection: Jdbc=jdbc:sqlserver://mydbserver:1437
 
Here the complete Log:

[2018-07-12 08:02:26] INFO: Flexmonster Data Speed Accelerator for Pentaho Mondrian 3.12
[2018-07-12 08:02:26] INFO: Version 2.5.6
[2018-07-12 08:02:26] INFO:
log4j:WARN No appenders could be found for logger (mondrian.olap.MondrianProperties).
log4j:WARN Please initialize the log4j system properly.
[2018-07-12 08:02:26] INFO: Reading config...
[2018-07-12 08:02:26] INFO: Reading config - OK
[2018-07-12 08:02:26] INFO: Loading JDBC driver...
[2018-07-12 08:02:26] INFO: Driver path: jar:file:./mssql-jdbc-6.2.1.jre8.jar!/
[2018-07-12 08:02:26] INFO: Driver class name: com.microsoft.sqlserver.jdbc.SQLServerDriver
[2018-07-12 08:02:26] INFO: Loading JDBC driver - OK
[2018-07-12 08:02:26] INFO:
[2018-07-12 08:02:26] INFO: Testing connection...
[2018-07-12 08:02:27] INFO: jdbc:sqlserver://mydbserver:1437;databaseName=mytestdb;user=myuser;password=mypwd
[2018-07-12 08:02:27] INFO: Data Source connection [mytestdb] - OK
[2018-07-12 08:02:27] INFO:
[2018-07-12 08:02:27] INFO: Starting server...
2018-07-12 08:02:27.347:INFO::main: Logging initialized @686ms
2018-07-12 08:02:27.378:INFO:oejs.Server:main: jetty-9.2.z-SNAPSHOT
2018-07-12 08:02:27.888:INFO:oejsh.ContextHandler:main: Started o.e.j.s.ServletContextHandler@4a194c39{/,null,AVAILABLE}
2018-07-12 08:02:27.920:INFO:oejs.ServerConnector:main: Started ServerConnector@42463763{HTTP/1.1}{0.0.0.0:50006}
2018-07-12 08:02:27.920:INFO:oejs.Server:main: Started @1261ms
[2018-07-12 08:02:27] INFO: Starting server - OK
[2018-07-12 08:02:27] INFO: Server is running at http://localhost:50006/
[2018-07-12 08:03:34] INFO: Handshaking... 2.5.6
[2018-07-12 08:03:34] INFO: Loading dimensions...
[2018-07-12 08:03:34] SEVERE: Mondrian Error:Internal error: Error while creating SQL connection: Jdbc=jdbc:sqlserver://mydbserver:1437
 
And here the configuration File:
CONNECTION_STRING=Jdbc=jdbc:sqlserver://mydbserver:1437;databaseName=mytestdb;user=myuser;password=mypwd;JdbcDrivers=com.microsoft.sqlserver.jdbc.SQLServerDriver;
JDBC_DRIVER_JAR=./mssql-jdbc-6.2.1.jre8.jar
JDBC_DRIVER_CLASS=com.microsoft.sqlserver.jdbc.SQLServerDriver
CATALOGS_PATH=./
PORT=50006
 
What I'm doing wrong? Thx for your support.