If the return hasn't been deposited on the expected date, first check the actual maturity date, the linked account, and whether it's a holiday or a workday.
Steps
Then check your account statement or the app.
If it still doesn't appear, contact the bank and specify the certificate name, the expected return amount, and the payment frequency.
A one-day delay due to a holiday isn't usually a problem, but if it continues, submit a follow-up request.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.