Despite receiving an IPO allotment, why did my UPI mandate fail?
Even though you have received your IPO allotment, the UPI mandate may fail due to technical challenges on your bank's end.

The registrar and the banks share an allotment file that shows which Money are deducted from the account. If the bank has technical difficulties, the debit will be re-attempted. The bank is responsible for ensuring that Money are debited from your account and transferred to the issuer's bank.

The shares credited to your Demat account will be accessible for sale on the listing date, even if your funds aren't debited.