Why won’t iCloud Keychain sync my passwords? I have set up two-factor authentication for my Apple ID and turned on iCloud Keychain. To test whether it backups my passwords, I turned it off and chose delete from iPhone. Then I turned it on and looked at my passwords, but nothing was there. I’ve tried many several times, but it seemed iCloud Keychain won’t store my passwords.

I think it might be because I turned it off, rather than signed out of my Apple ID, or it might be something wrong with my iCloud configuration.

Please help me resolve this problem.
If you have no other Apple devices, then when you chose to delete your passwords, you likely deleted them from your phone (at first).  But when you re-enabled iCloud, you synced your current phone status to iCloud, which is / was password-less and removed the content from iCloud as well.