A Paprika Cloud Sync account is required to sync your recipes between devices. The first thing to check is to make sure you are logged into Paprika Cloud Sync on all of your devices. This is accessed by going to Paprika's Settings -> Paprika Cloud Sync. If you already have an account, log into your existing account there. If you don't have an account, you can also create one there.
The second thing to check is to make sure that you are logged into the same account on all of your devices. Recipes are linked to a specific Paprika Cloud Sync account. Most of the time when someone encounters this issue, it is because they have accidentally logged into different Paprika Cloud Sync accounts on each of their devices. Make sure the email addresses match exactly. We often find cases where there is a typo somewhere in the email address, or where the domains do not match (e.g. firstname.lastname@example.org vs email@example.com).
If you have found that your email addresses do not match, you can correct this by logging out of the incorrect account, and then logging in with the correct email address. Also, if you have recently reset your password, you will have to log out and log back in with the new password on all of your devices.
(Paprika does not use iCloud for syncing, so your iCloud account will not affect Paprika Cloud Sync in any way.)