language "plpgsql" does not exist

i am trying to create functions only to get the above error in return.
what do i need to do to get PL/PGSQL functions working?
example:

CREATE FUNCTION logfunc1(text) RETURNS timestamp AS '    DECLARE        logtxt ALIAS FOR $1;    BEGIN        INSERT
INTOlogtable VALUES (logtxt, ''now'');        RETURN ''now'';    END;
 
' LANGUAGE plpgsql;

#  ERROR:  language "plpgsql" does not exist


any help appreciated


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