If I type command-\ to fill my username/password, 1password prompts me for my vault password, then shows me the 1password UI, and doesn't fill the form.
Now that I've unlocked it, if I focus back on the web page, and command-\, it fills the form just fine.
1Password Version: 1Password 7 Version 7.0 (70000019) AgileBits Store
Extension Version: 220.127.116.11
OS Version: OS X 10.13.4
Sync Type: Dropbox
Referrer: forum-search:signing in interrupts command-\ operation