Flo Premium is connected to your Apple ID/Google account, not to your Flo account.
If your email address is not recognized by the app, it might be that you have been using the app anonymously. If this is the case, unfortunately, there is no way to restore your data and you’ll need to start from the beginning and register your account: Menu > Profile (this is an additional step for Android users) > Continue. After you register your new account, you’ll be able to restore your data at any time if your device is changed, lost, damaged, or reset.
If you’re using the same Apple ID/Google account that you used to make a purchase and have an active subscription, all accounts you create in Flo will be Premium.