Issue: When creating a new user, the invite link generated by odoo targets the first website in a multi-website configuration (odoo reads the system parameter value from ).
Solution: The correct way to generate the invite link when multiple websites are configured is to ensure that the "website field" (found in the "Sales & Purchase" tab, "Misc" section) is correctly set to the appropriate website. In this case odoo will build the final URL using this value.