Carrying forward SQL

I have a query gets opening and closing balances for each month of customers from their transactions and then get a company total for the month. but if a customer does not have any transactions for multiple months i need to get the last closing and use it to fill all empty months.. right now im using LAG to get the last closing balance before any empty but when i carry that forward i can only carry it forward into 1 empty month which results in incorect calculation of the company's total... any help will be appreciated.

found that this is line made my query working for anybody that care.

customer_month_balances AS (
    -- Combine customer-month combinations with their balances
    SELECT
        pm."customer_id",
        pm."month",
        COALESCE(mb."month_opening_balance", NULL) AS "month_opening_balance",
        COALESCE(mb."month_closing_balance", NULL) AS "month_closing_balance"
    FROM
        customer_months pm
    LEFT JOIN
        monthly_balances mb
        ON pm."customer_id" = mb."customer_id"
        AND pm."month" = mb."month"
),
propagated_balances AS (
    
    SELECT
        customer_id,
        month,
        month_opening_balance,
        month_closing_balance,
        LAST_VALUE(month_closing_balance IGNORE NULLS) OVER (
            PARTITION BY customer_id
            ORDER BY month ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW
        ) AS propagated_closing_balance
    FROM
        customer_month_balances
)