Cookies with maxAge Set Do Not Persist

I am attempting to use an httpOnly cookie with the maxAge property set in order to persist a session even when the app is restarted. I'm finding that the cookie disappears on app closure. Most posted fixes for this out there recommend the use of localStorage, which is definitely a bad idea for an auth cookie. I am not having this issue in Android, so I suspect it's WKWebView that's the issue.