Invalid column name UsrBalance

Please check if you have the value of system setting called "Prefix for object name" set as Usr and if it is not - you need to change it to Usr and relogin to the system and check the issue after that.

If it won't work, please try to find this column in the database and if it is not present in the database - please run update database structure for the object which is represented by the table where this column is present.

Also please double check if the field was added the same way to this part in the article:

define("OrderPageV2", [], function() {
    return {
        // Edit page object schema name.
        entitySchemaName: "Order",
        details: /**SCHEMA_DETAILS*/{}/**SCHEMA_DETAILS*/,
        // The attributes property of the view model.
        attributes: {
            // Name of the view model attribute.
            "UsrBalance": {
                // Data type of the view model column.
                dataValueType: Terrasoft.DataValueType.FLOAT,
                // Array of configuration objects that determines [UsrBalance] column dependencies.
                dependencies: [
                    {
                        // The value in the [UsrBalance] column depends on the [Amount] 
                        // and [PaymentAmount] columns.
                        columns: ["Amount", "PaymentAmount"],
                        // Handler method, which is called on modifying the value of the on of the columns: [Amount] 
                        // and [PaymentAmount].
                        methodName: "calculateBalance"
                    }
                ]
            }
        },
        // Collection of the edit page view model methods.
        methods: {
            // Overriding the base Terrasoft.BasePageV2.onEntityInitialized method, which 
            // is triggerd after the edit page object schema has been initialized.
            onEntityInitialized: function() {
                // Method parent implementation is called.
                this.callParent(arguments);
                // Calling the handler method, which calculates the value in the [UsrBalance] column.
                this.calculateBalance();
            },
            // Handler method that calculates the value in the [UsrBalance] column.
            calculateBalance: function() {
                // Checking whether the [Amount] and [PaymentAmount] columns are initialized
                // when the edit page is opened. If not, then zero values are set for them.
                var amount = this.get("Amount");
                if (!amount) {
                    amount = 0;
                }
                var paymentAmount = this.get("PaymentAmount");
                if (!paymentAmount) {
                    paymentAmount = 0;
                }
                // Calculating the margin between the values in the [Amount] and [PaymentAmount] columns.
                var result = amount - paymentAmount;
                // The calculation result is set as the value in the [UsrBalance] column.
                this.set("UsrBalance", result);
            }
        },
        // Visual display of the [UsrBalance] column on the edit page.
        diff: /**SCHEMA_DIFF*/[
            {
                "operation": "insert",
                "parentName": "Header",
                "propertyName": "items",
                "name": "UsrBalance",
                "values": {
                    "bindTo": "UsrBalance",
                    "layout": {"column": 12, "row": 2, "colSpan": 12}
                }
            }
        ]/**SCHEMA_DIFF*/
    };
});