Did BitGo terminate its "BitGO instant" service? Why? This is the launch announcement.

https://www.bitgo.com/instant is a dead link now.
I can't say for sure, as I don't use the service, but the current page appears to be here: https://www.bitgo.com/info/solutions#instant .  It's linked in the Solutions menu on the header of every page, so they're not hiding it.