Note that if it is this app -> https://apps.apple.com/us/app/ipassword-password-manager/id730254788 the developer last updated it a year ago. But there are at least two other apps also named iPassword. It does look like all the developers of such named apps are still active so you need to contact the developer of your particular “iPassword” app and ask them to fix their code.
You may also want to move away from these small personal developer’s password apps. They are notorious on these forums over the years for abandoning their apps and leaving people with locked data and no way to unlock it. There are several well regarded password apps from larger software companies that have been around for years and have always kept their apps current for iOS, iPadOS, MacOS and Windows (examples are apps like 1Password by AgileBits Inc., or mSecure by mSeven Software LLC, NortonLifeLock Inc also makes one). You’re just more likely to never have the issue of an unsupported encryption app if you stick with larger companies who have been producing, selling and supporting their app for a very long time and who have far more clients than many of the short term come and go password vault type apps from individuals (there have been hundreds of such apps that have appeared, and then disappeared over the years, and every iOS update, one or more gets broken because they’ve been dropped by their developer).