The message should include the error message returned from $modx->db->getLastError(). This clearly doesn’t return anything useful that’s why you’re not seeing anything after "Reason is:"
Firstly check that you have a "{table_prefix}dbedit_configs" in your database. (where {table_prefix} is the modx table prefix as set during modx installation). dbEdit should automatically create the table but if it’s not there you may have to create it yourself.
CREATE TABLE `{table_prefix}dbedit_configs` (`recID` TINYINT (3) UNSIGNED AUTO_INCREMENT, `name` VARCHAR (128) NOT NULL, `comment` VARCHAR (255) NOT NULL, `config` TEXT NOT NULL, PRIMARY KEY(`recID`), UNIQUE(`name`)); (again replace {table_prefix} with the actual modx table prefix).
Also check that this table is readable by the mysql user that you have configured for modx.