I've configured an SCCM installation in my lab. I enabled client push, and in that process, assigned a newly created service account as the account to use to push the client. I waited about 15 minutes or so, and I'm seeing warnings under SMS_Client_Config_Manager component status, saying access is denied. I've now changed the credentials being used to another account, that's been around since the beginning, and should work. My question: Will the client push automatically go again, and if so, when? If not, do I need to right-click the machines in the collection and manually push the client?

The push will be automatically retried once every hour (up to one week). You can speed that up by copying the .ccr files from \ccrretry.box to \ccr.box.