Field Service is a Salesforce product that enables companies to manage work orders, service appointments, service resources, and service territories. It also provides features such as scheduling optimization, mobile access, and offline support. Field Service is the recommended functionality for scheduling repair service when an agent is unable to solve the customer's problem via the call center. Verified References: Service Cloud Consultant Certification Guide & Tips, Field Service Overview

Explanation
Experience Cloud with Customer Account Portal template is the recommended solution to meet the requirements of reducing service costs and improving customer relationship by allowing customers to pay invoices and update their contact information online. Experience Cloud is a product that allows you to create branded online portals for your customers, partners, or employees. Experience Cloud sites can provide self-service resources, such as knowledge articles, FAQs, forums, and case management. Customer Account Portal is a template that provides a pre-built site for customers to access their account information, such as invoices, payments, orders, contracts, or contact details. Customers can also update their profile, preferences, or communication settings from the site. Verified References: Service Cloud Consultant Certification Guide & Tips, Experience Cloud Overview, Customer Account Portal Template Overview

Verifying that users are assigned the Chat feature license is the configuration option that should be verified if agents cannot see the Chat footer component in the Service Console. A Chat feature license is a type of license that enables users to access Chat functionality, such as initiating, receiving, transferring, or ending chat sessions, sending quick texts or files, or viewing chat reports. Users must have a Chat feature license assigned to their user record in order to use Chat in the Service Console. Verified References: Service Cloud Consultant Certification Guide & Tips, Assign Chat Licenses

These are two reasons why the integration is failing after migrating from Classic Knowledge to Lightning Knowledge. The URL formats for articles change when migrating from Classic Knowledge to Lightning Knowledge, so any integration that relies on URLs needs to be updated accordingly. Also, users need to have Modify All permission on the article type object to delete archived articles in Lightning Knowledge, whereas in Classic Knowledge they only needed Delete permission on the article type object. Verified References: :
URL Formats for Articles Change When Migrating from Classic Knowledge to Lightning Knowledge : Delete Archived Articles in Lightning Knowledge