I noticed this on back on my iOS 10 iPhone 6 whatever 1P it was, and on the latest 1P on my iPhone 8 iOS 11.0.3, was hoping new iOS/new 1P would solve this but I have an issue where a new login entry directly in 1P App (not in the browser), does not save.
+sign in upper corner
— and i'm checking All vaults too
On the desktop, i can create a new login, it will sync to mobile and i can use it almost immediately, so i know sync works and i know creating new works on the desktop .
1Password Version: 6.9.1
Extension Version: Not Provided
OS Version: iOS 11.0.3
Sync Type: subscribed