Does anyone have experience in diagnosing ip-https on a DirectAccess server?

Question

Windows Server

Good afternoon.
Faced such a situation, there is a DA server (win 2012r2), configured via 1 nic, edge and all clients work via ip-https.
One fine day, all clients (win 10 ent) stopped receiving ipv6 prefix from the DA server.
Both the server and clients report that iphttpsInterface started without errors.
The connection to https:// domainname :443/IPHTTPS goes through. The resource is available.
The certificates are ok. Firewall too.
But since the client does not receive an ipv6 prefix, it cannot configure SA.
This article did not help: https://technet.microsoft.com/ru-ru/library/ee8441...
Since there is no address on other ipv6 interfaces either, not to mention white ipv4.

Answer 1

netsh interface ipv6 reset solves the problem.
It remains to understand what causes it.