Pgbackrest - conflict between 'main' and 'demo'

This is a 'pgbackrest' question. Please let me know if this is not the
correct group for such a query.

I am attempting to follow the guide
(https://pgbackrest.org/user-guide.html) which creates a 'demo' cluster
and then configures it.

Everything is fine until I run: sudo -u postgres pgbackrest --stanza=demo
--log-level-console=info stanza-create

The error is:

INFO: stanza-create command begin 2.25dev: --log-level-console=info
--pg1-path=/var/lib/postgresql/10/demo --repo1-path=/var/lib/pgbackrest
--stanza=demo
ERROR: [058]: version '10' and path '/var/lib/postgresql/10/main' queried
from cluster do not match version '10' and '/var/lib/postgresql/10/demo'
read from '/var/lib/postgresql/10/demo/global/pg_control'
HINT: the pg1-path and pg1-port settings likely reference different clusters.
INFO: stanza-create command end: aborted with exception [058]

I don't understand how to edit the "read from cluster" in order to set it
to /var/lib/postgresql/10/demo

I have modified every entry in the data_directory in
/etc/postgresql/10/main/postgresql.conf to point to
/var/lib/postgresql/10/demo but that didn't change anything.

My /etc/pgbackrest/pgbackrest.conf shows:

[demo]
pg1-path=/var/lib/postgresql/10/demo

[global]
repo1-path=/var/lib/pgbackrest

Can anyone please advise me how to fix this error, thanks?