Why Juju agent not installed while juju add-machine

i have maas with juju, and have add the machine to maas, then setup storage, network, tags, etc and the machine has been successfully commisioning. Then run juju add-machine, the os is installed but if I check from juju the machine status is still pending Deployed, then I ssh to the machine find juju agent has not been installed at all and this only happens on some machine nodes, and If you compare cloud-init .log machine which is successful with pending machine, it turns out that in cloud-init.log the initialization of the pending machine process does not run perfectly. Why this happened? is there any problem with MAAS or with Juju Controller?

and has anyone experienced the same thing with my case?