One of the line in the message log reads "Connection refused.". Check:
1. MSSQL is set to use SQL Authentication.
2. JAVA_HOME is auto-detected by the app while setting it up after installation.
3. If using DBX 1.1.7, use jre7u or jre8u45 for DBX 2.0.x
Pls share what OS/SQLver/JREv are you have in your setup.