If your InstaPay account has been blocked due to IPN PIN attempts, open the official app, go to Manage Accounts, then select Forgot/Unblock IPN PIN.
Steps
Complete the verification steps and set a new PIN.
Do not ask anyone to "unblock" your account, and do not share your OTP or card details.
If the in-app unblocking process fails, or the problem is related to account registration or a financial transaction, contact your bank; InstaPay itself forwards these cases to the bank.
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.