I have a RouterBoard 951Ui-2HnD (RouterOS 6.45.9) which has been set up - and had been working - with an SSTP VPN. I don’t think that I changed anything (other than routine RouterOS updates; I’m on the long-term channel). The SSTP VPN stopped working.
How is the title of the topic related to the description? Other than that, do you use certificates for SSTP, maybe it has expired?