Notes - empty folder on iPhone but ok in iCloud and on iPad - how do I resolve?

This is very simple and everyone I've helped comes back to say it worked:

Open the Settings App

Tap your name at the top

Tap iCloud

Look for Notes and turn the switch on. If already on, turn it off, then back on again

Boom, your notes will redownload to your iPhone.

Try logging in your iCloud account by going to iCloud and turning Notes on, but first set an e-mail going through Notes (Settings -> Apps -> Notes), go to “Notes Accounts” and in “Add Account” to set a new e-mail.