I have tested this website and have not been able to recreate the issue, I was able to autofill, drag and drop and copy and paste the credentials into the fields.
The following steps should help to resolve the issue:
- Open your 1Password, locate the login entry for this website and delete it from your 1Password (make sure to copy the username and password to a temporary location beforehand if you don't remember them by heart).
- Go to the website that is not filling and complete the login fields (do not press return or click sign in).
- Right click on the 1Password icon in your browser toolbar
- Click 'Save Login'.
- Select a vault, give the login a title, then click Save.
- Revisit the website login and you should see the inline autofill menu in the fields.