I had the same problem, the solution proposed by @Grimroper solved it with a minor change: there is no public_html directory in v.1.2.32, for me this works:
/usr/local/bin/php /home/*path-to-kanboard*/cli cronjob >/dev/null 2>&1
instead of
/usr/local/bin/php /home/*path-to-kanboard*/public_html/cli cronjob >/dev/null 2>&1