Agent Update 11.2.3a never start

Hello,

I have strated to deploy 11.2.3a on managed devices.
I noticied that with some devices the update never start.
Version is 11.2.2 MU2 on Windows 7 x64 SP1 FR
I did :

zac cc, zac ref serveral times, rebooted, zac unr and zac reg on a device but nothing to do.

Any idea?

Thanks in advance.