Office Activation Required with valid ID

I have a valid VLSC with Microsoft but for the last month users are getting Activation is required with Office 2013.  When I put in my activation code it tells me that it can't validate it to call MS to get a valid number.  They assist me with a valid number but will not tell me why it's happening.  Do you have any insight on what's wrong so I can fix it.

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JohnBusiness Consultant (Owner)Commented:
You will have a receipt from Microsoft or a reseller. Call Microsoft Licensing Support with this and ask why.

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You should be able to log into your account at the Volume Licensing Center.  What does it show for the key?

Sometimes keys get re-sold many times and eventually get locked by Microsoft.  That may or may not be the case here.
Dr. KlahnPrincipal Software EngineerCommented:
I tend to agree with CompProbSolv' speculation on the cause.  All it would take is for one person to run a keyfinder on their work PC.  They would then have the VLK to use on all their own systems, and from there it's an easy jump for the key to get out on the internet.
The two answers provide a reasonable solution to the issue.
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