I have the 1Password 7.2.2 Desktop client installed, and the "1Password extension (Desktop app required)" extension in Chrome installed (version 18.104.22.168). Running the latest macOS 10.14.2.
After a recent update it seems that forms will no longer fill for subdomains (xyz.example.com) when only the domain (example.com) is registered as the login's website.
For example, if I browse to 'xyz.domain.com' and the website 'https://domain.com' is saved for a login, 1Password will no longer fill the login details into the form on xyz.domain.com. Instead, it will open a new tab and navigate to https://domain.com. To temporarily resolve this, I had to add in each individual subdomain so 1Password can fill the form with the login details.
Note: Just tested this in Safari (latest extension installed in Safari) and it looks like this is not an issue in Safari.