Use the alerts unacknowledge command to unacknowledge an alert.
crcli alerts unacknowledge --alertuid <alert ID>
[root@cr-system]# crcli alerts unacknowledge --alertuid 60510164f37bd2000199380f, 60510069f37bd2000199380c Alert: 60510164f37bd2000199380f,60510069f37bd2000199380c unacknowledged successfully. [root@cr-system]#