Earlier quoted context omitted.
I'm pretty sure you can access all your passwords offline. So not sure what os/version you are using... but you might ask 1Password support about why that's not working for you.
I may have misspoken and been referring to secure attachments - I'll check. (This is on my iPhone). I'm sure I've been in situations where I am trying to download a travel permit for example at a check in desk overseas and there is no signal. I'll see if passwords are the same - maybe those are indeed kept locally.
1. Add a new 1Password item on device 1
2. Do _not_ open the 1Password app on device 2
3. At some point/the next day or whatever, device 2 goes offline
4. Now, while offline, you do not have access to the new item on device 2 because data wasn't synced because the 1Password app hasn't been opened after #1.
The problem seems, 1Password doesn't sync the data in the background (iCloud in my case.)
However, if you did sync by manually opening the app while online, all data will also be available offline later (including attachments.)