KMS host Office 2010 not found - is missing?

I had strange case - once upon a time my KMS host has stopped processing requests from clients or, if reading strictly messages, clients couldn't find KMS host.

Installed product key detected - attempting to activate the following product:
SKU ID: 9da2a678-fb6b-....-....-........819a
LICENSE NAME: Office 14, OfficeStandard-KMS_Client edition
LICENSE DESCRIPTION: Office 14, VOLUME_KMSCLIENT channel
Last 5 characters of installed product key: 8R6BM
ERROR CODE: 0xC004F074
ERROR DESCRIPTION: The Software Licensing Service reported that the computer cou
ld not be activated. No Key Management Service (KMS) could be contacted. Please
see the Application Event Log for additional information.

At first I thought that it was connected with second _vlmcs._tcp.current.domain record - I have two records - one for Windows 2008R2 with activation keys for Windows 7/10, Office 2010 (14), Office 2013 (15) and Office 2016 (16), and the second KMS on Windows 2016 with activation for Windows 2016 servers. I can't discover KMS by Active Directory - I haven't schema extended to Windows 2012R2 so I'm tightened with DNS discovery. So I removed DNS record poiting to KMS on Windows 2016 but without result.
Using slmgr.vbs /dli all I received confirmation that I've got Office 2010 key, but clients are looking for activation for Office 14 which, actually, isn't activated on KMS host. I didn't think about reregistration of KMS for Office 2010 because - it was working few days ago and Office 2010 key was still activated.
I made a call to Microsoft, registered a case with result that I must done reactivation/reregistration of Office 2010 KMS Host. I did it and now it is working.