In general, the mandate SMS or notification is triggered within a few minutes of the bid placed. However, at times, there may be a delay due to technical issues at NPCI. If you have not received an SMS or notification for amount-blocking even after six hours of placing your bid, you may have to apply again.
To do this, login to Upstox, delete your application, and reapply. This will trigger the amount-blocking-related SMS/notification on your UPI app.