operator does not exist: timestamp with time zone + integer in PostgreSql
Maybe someone created the operator with those types in one database, but not in the other one.

create function addit(timestamptz,int) returns timestamptz immutable language sql as $$ 
    select $1+ interval '1 day'*$2 
$$;
create operator + (leftarg =timestamptz, rightarg =int, procedure=addit);