Client not updating though client install package applied

Hi,

I have recently upgraded my SEPM to 14.2 MP1 (14.2.1015.0100). I have then assigned the client install package since 19/11, but until now the clients have not been upgraded automatically. Clients are on 14.0.3897.1101; some have upgrade but some not upgraded. When I check the client on SEPM Deployment status is stuck on The client is ready to accept the upgrade package. How can I troubleshoot this? Anyway I can force it?

Thanks to help!