The User Presence Properties are set to true but still the feature is not working. 

• Your avatar on the header doesn't show a green dot on the home page:
  
  
  
  
• When two users are watching the same record, user presence is not visible on the header of the form:
  
  

Jakarta - UI16

• The correct user presence property is not enabled
• After the presence property is enabled, browser cache is not cleared

1. Make sure the value of the system property 'glide.ui.presence.disabled' is false:
   https://<your_instance_name>.service-now.com/sys_properties_list.do?sysparm_query=name%3Dglide.ui.presence.disabled&sysparm_first_row=1&sysparm_view=
2. Clear browser cache to see the change. User presence works only if the browser cache is cleared after the property is enabled.

• If you want to read more about why you need to flush browser cache to see the change read more about it in this article: User presence works only if the browser cache is cleared
• Here you can read more about this system property: Disable user presence
• Read more about presence: User presence