Postgres error

Hello Guys,

I have case of two Postgres version 11 ( replication using repmgr) and and
its work fine as below:
-bash-4.2$ sudo su - postgres -c " /usr/pgsql-11/bin/repmgr -f
/var/lib/pgsql/repmgr/repmgr.conf cluster show"
ID | Name | Role | Status | Upstream | Location | Priority |
Connection string
----+-------+---------+-----------+----------+----------+----------+--------------------------------------
1 | pgdb1 | standby | running | pgdb2 | default | 100 |
host=pgdb1 user=repmgr dbname=repmgr
2 | pgdb2 | primary | * running | | default | 100 |
host=pgdb2 user=repmgr dbname=repmgr

but when I installed pgpool 4.1 on third server to loadbalace the traffic
., from command line I see everything ok like below:

-bash-4.2$ psql -U pgpool --dbname=postgres --host pgpool -c "show
pool_nodes"
node_id | hostname | port | status | lb_weight | role | select_cnt |
load_balance_node | replication_delay | replication_state |
replication_sync_state | last_statu
s_change
---------+----------+------+--------+-----------+---------+------------+-------------------+-------------------+-------------------+------------------------+-----------
----------
0 | pgdb1 | 5432 | up | 0.500000 | standby | 0 |
false | 0 | |
| 2020-02-17
11:03:31
1 | pgdb2 | 5432 | up | 0.500000 | primary | 3 |
true | 0 | |
| 2020-02-17
11:03:31

the problem is appears on when i installed pgpooladmin and tried to stop
one node ( master os slave ) I got the below error on pgserver ( not
pgpool)

2020-02-17 10:49:39.118 IST [2051] ERROR: function pgpool_pgctl(unknown,
unknown) does not exist at character 8
2020-02-17 10:49:39.118 IST [2051] HINT: No function matches the given
name and argument types. You might need to add explicit type casts.
2020-02-17 10:49:39.118 IST [2051] STATEMENT: SELECT pgpool_pgctl('stop',
's')

what I can do please