On August 11th, YouTube announced some changes to its API policies, which will impact all integration partners, including Hootsuite. One of the changes announced is the deprecation of the API endpoint used to power the My Subscriptions stream in the Hootsuite dashboard.
As a result, new My Subscriptions streams can no longer be added to the Hootsuite dashboard. Users who already have the stream installed will continue to have access until September 12, 2016, when it will be removed from all dashboards.
Hootsuite users will still be able to subscribe and unsubscribe to other YouTube channels from all other YouTube streams.