ERROR: function dblink_connect(unknown) does not exist

PostgreSQL Link from another database

Activate function DBlink :

CREATE EXTENSION dblink;

---

Connection Link Query :

 select dblink_connect('host=servername user=username password=password dbname=databasename')  ;

Result :
OK

---

Select from another database Query :

SELECT *
    FROM dblink('host=servername user=username password=password dbname=databasename', 'select column1, column2 from TableProductMaster ')
      AS t1(Column1 text, Column2 text) -- as field and field type
    WHERE column1 LIKE '%556%'  -- as Condition
    Order by Column1 Asc;


Result :
Column 1    | Column2
A|1
B|2
C|3


Thank You