sp_getapplock not working in multiple Connection
Detailing the answer added to the question, according to the sp_getapplock documentation, (emphasis added):


  The lock resource created by sp_getapplock is created in the current
  database for the session. Each lock resource is identified by the
  combined values of: 




  The database ID of the database containing the lock resource.


  The database principle specified in the @DbPrincipal parameter.


  The lock name specified in the @Resource parameter.