@Goodluck Sometimes, due to technical issues from your bank’s end, the UPI mandate might fail even if you have received the IPO allotment.
The registrar shares an allotment file with the banks based on which funds are debited from the account. In case the bank is facing technical issues, it will re-attempt the debit. The onus is on the bank to ensure that funds are debited from your bank account and given to the issuer’s bank.
Even if your funds aren't debited, the shares credited to your demat account will be available for selling on the listing date.
So keep balance in your bank.