my 1Password has stopped syncing

I'm using 10.8.44 on an iMac, iPhone, and MacBook Air. I've been thinking that passwords I've created or changed recently, are not changed on another device. Today, I had my suspicions confirmed. I couldn't find the password for a site I use often.I searched 1Password and it just wasn't there. I looked on my other devices and it had vanished everywhere. I went to the website and clicked I forgot. Went through the whole process of changing the password and saving it. The site wanted me to sign in with it on a different device. So I tried, but couldn't find that item on the different device. I had to go through the whole process again. And again. Finally, I had to manually create the login on all my computers. 1Password has always synced reliably. How can I make it sync?

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