If you have trouble pushing out the SCCM Client to a workstation, you should first check the CCM.log on your SCCM Server.
The best tool to do this is cmtrace.exe which is found in the “tools” folder of your SCCM server.
If you detect an error like “ERROR: Site xxx is trying to install SMS Client on machine xxx. Can not push client to this machine for 24 hours.”
you will have to remove the client install lockfile
\\PCName\admin$\SMSClientInstall.XXX where XXX stands for your site code.
Also the folder \\PCName\admin$\ccmsetup has to be deleted.
After that, the installation should be working. 🙂
In my case this error occured because the new machine was shut down during the first moments of the client installation.