There’s an extra step to required to enable the browser extension to communicate with the desktop application. I found a few old post on the 1Password Support Bulletin Board where some instructions have been pasted. It’s still necessary today in Feb 2025 to create a file at /etc/1password/custom_allowed_browsers with the executable name of the browser to trust. In this case, vivaldi-bin. The file mode of 0644 is fine. I don’t know why the suggestion was made to make the configuration file executable.