I've had the same problem over the last two months. Only one of the five games from this month's subscription cycle will start (Overkill VR) the others (AI Rebellion VR, HordeZ, ROM Extraction, and Sairento VR) will start to launch, but fail after a minute long pause with no error messages or dialog boxes. I worked with the online chat support yesterday for over 3 hours deleting and reinstalling the Viveport App and all games, but launching subscribed apps still is not working correctly (success of one app in the last ten subscribed apps so far).
I have no problems downloading and launching Steam apps and have more than 50% drive space free and anti-virus disabled.
The Vive support form on the "contactus" page seems to go nowhere. I have sent four separate web form support request about the issue through the Vive support over last two months, but have not received any response. The form is currently broken. You are required to enter a Captcha in the last field of their form, but the captcha generator link is not working and just displays a broken image link icon.
I think it might be time to give up and cancel the subscription. Hopfully they will work-out the bugs and I could give it another try in the future. It could have been great.