Lost Favorites + cannot add Favourites

[Rob-1512]

Since updating to the latest Metamask version 3.3.0 on iPhone all my Metamask Favourites have disappeared. It is no longer possible to add Favourites in Metamask. In addition I can no longer add custom tokens.
The problem occurred while being on iOS 14.7, I'm now on 14.8
I have uninstalled and reinstalled Metamask but the problem remains.
How can this be fixed ?