Hey MVRLon,
Firstly, I must apologise that it has taken so long for you to receive a response on here.
I'm sorry for the trouble you are having, we have done some testing and have been able to re-create the behaviour you are seeing. It looks like the behaviour is limited to Firefox only, and happens only when 1Password is locked. If 1Password is unlocked when we try and fill with Cmd + \, the fill acts as expected. I've created a report to have our development team look a little further into what might be going wrong, and I've added your insights in support of this investigation.
In the meantime, could you try the following workaround to fill your login (when 1Password is locked)?
- Navigate to the website you'd like to fill.
- See that 1Password is locked.
- Press Cmd + Shift + Space to invoke the Quick Access prompt.
- Unlock your 1Password account.
- You should then see the Quick Access prompt, press Return on your login item listed to autofill on the webpage.
I realize this extra step might not be as ideal as using the Cmd + \ to fill, and I'm sorry for any interruption in your workflow. Let us know if you have any questions!
ref: dev/core/core#19106