VAMT and Office 2010 activation

Hi,

I have a VAMT server used to activate many Office 2010 with KMS key in our domain.

I installed last valid KMS key on server.

Since last month we have a problem, when we add a new PC on our domain, if we try to activate the office 2010 on server I don't see any error message. On client the office result not activated. Microsoft says me that the product ID was blocked.

Why? We are using this VAMT server in the last 8 years without problems.

Best Regards