Zerodha only accepts bids on behalf of the client, forwards it to the Exchange. Here’s how the flow works:
Our team is in constant touch with the Exchange and since IPO through UPI is in it’s nascent stage, there could be teething issues. If you are having trouble doing it through our platform, suggest you use the bank’s portal and apply. Here’s more on how to do it How to apply for an IPO with your Zerodha account? - #2 by Bhuvan