You do not have cgroups v2. Setup cgroups:
1.Using drop-In files method
For each user you wish to configure, you will need to create a directory in mkdir /etc/systemd/system/user-UID.slice.d. e.g.mkdir /etc/systemd/system/wordpressuser-1001.slice.d
$ cd /etc/systemd/system/wordpressuser-1001.slice.d
echo "[Slice]" >> 50-TasksMax.conf
echo "TasksMax=10%" >> 50-TasksMax.conf
Validate the file changes by running cat 50-TasksMax.conf
To use cgroups with OpenLiteSpeed you need to install glib as root.
RedHat/Centos: sudo yum install glib2
Ubuntu: sudo apt-get install glib2.0
In OLS WebAdmin, configure OpenLiteSpeed to have CGI apps use the user ID of the owner of the file. Navigate to Configuration > Virtual Hosts > and select the virtual host you wish to manage. In the Basic tab, modify the Security entry and set the ExtApp Set UID Mode to CGI File UID
To enable cgroups at the server level, in OpenLiteSpeed WebAdmin, navigate to Server Configuration > Security , edit the CGI Settings group and enable cgroups by setting it to on
Note: Avoid systemctl configuration if you see it in any tutorial in the web