wsrep_cluster_size remains zero

Installed Galera cluster on an ubuntu 20.04 server, using these instructions: https://galeracluster.com/2021/03/installing-galera-4-with-mysql-8-on-ubuntu-20-04/

But after installation, when I run "mysql -uroot -p -e "show status like 'wsrep_cluster_size'" " I always get:

+--------------------+-------+ | Variable_name | Value | +--------------------+-------+ | wsrep_cluster_size | 0 |

So the cluster does not start.

sudo aa-status gives nothing for mysql, as I disabled apparmor for mysql using these: How to disable AppArmor for MySQL

/etc/mysql/mysql.conf.d/mysqld.cnf is like this:

[mysqld]

pid-file        = /var/run/mysqld/mysqld.pid
socket          = /var/run/mysqld/mysqld.sock
datadir         = /var/lib/mysql
log-error       = /var/log/mysql/error.log
binlog_format=ROW
default-storage-engine=innodb
innodb_autoinc_lock_mode=2
bind-address=192.168.1.2

# Galera Provider Configuration
wsrep_on=ON
wsrep_provider=/usr/lib/galera/libgalera_smm.so
# #
# # # Galera Cluster Configuration
wsrep_cluster_name=flog
wsrep_cluster_address=gcomm://192.168.1.2,192.168.1.3,192.168.1.4
# #
# # Galera Synchronization Configuration
wsrep_sst_method=rsync
# #
# # Galera Node Configuration
wsrep_node_address=192.168.1.2
## This is first node

Solved: /etc/mysql/my.cnf was missing this line:

!includedir /etc/mysql/mysql.conf.d/

Actually I had commented the line out, since I thought the ! would mean negation. i.e. exclude the directory.