kriswegrijden Kindly view screenshot in chrome and firefox wherein Facebook like icon can be seen however you will require to configure the facebook settings as per documentation link shared wherein details are required to be populated in respective fields in order for it to function properly. Ref : Screenshot for the same
You may check if any add-on or blocker has been enabled for your browser which may be blocking the button like mentioned here. To troubleshoot also, Try to check in other computer systems