Technical support is suddenly being flood by similar situations. It needs to be dealt with on steam's end as we don't have any control over Steam's licensing server. Especially in last weekend many reports of this got delivered.
I did ask the devs about it though, perhaps they know about this issue.
My current advice is to contact Steam's customer support.
The developers confirmed that this is a steam related issue. You will need to contact their customer support at www.steampowered.com
It's not the first time Steam has server related issues keeping people from playing games, How many times I have received the "No steam servers available", "This game is currently unavailable", "cannot go offline because steam cannot
connect" to many different games. It's truly frustrating since you paid money for a product you are unable to play because their servers are "busy" And in this case, VSTEP get's the blame for this.
Try to follow any of their steps on their support page:
https://support.steampowered.com/kb_article.php?ref=2204-OPGC-4862
Especially the last step could be interesting. This method fixed many of my steam problems.
Just for the record, this issue is not only isolated to SSE.