I opened this bug on Wavebox over a year ago thinking it was something that was happening in their implementation, but it's present in all browsers.
When attempting to log into a site that opens a popup window (prevalent in desktop apps, for instance), you're not able to open the 1Password extension without first switching to a normal browser window and activating either the toolbar button or hotkey.
It's unclear to me why the hotkeys don't work when the toolbar is missing, but it's definitely true. Behavior is constant across platforms, browsers, versions of 1P app, and extensions.
1Password Version: 7.8.820 (win), 7.8.7 (mac)
Extension Version: 2.1.3
OS Version: Windows (10, 11), macOS