[SEPM] Certificate acknowledgement prompt at logon

Hi all,

I have upgraded 2 SEPM servers from 12.1 RU4 to RU6 MP1a.

Everything went ok, no problem.

Now I've exited the console and I want to logon again.

Before login, the console tells me that the certificate is not in the store and prompts me for the acknowledgement.

Where does this come from ?

I suppose there's no security problem but I don't understand why I'm prompted today ?

Last year I've upgraded from RU1 to RU4 and I don't remember having had this annoyance.

Thanks for your answers.

Luc