In February I took advantage of replacing my Roku 2XD model 3050X when Roku notified me that it would no longer be supported after 12/31/19. This Roku had HBO GO installed on my LG living room TV.
Roku sent me a Roku Express+ model 3910x which I activated on my LG living room TV.
I took the Roku 2XD and set up and activated it on the Philips TV in my office. (This Philips TV was originally in the living room until we replaced it with the LG TV. The Roku 2HD was used on this Philips TV when it was in the living room.)
I just became aware of HBO GO not listed in my HOME menu on the Roku 2XD. When I try to add channel HBO GO I get "Channel install failed - Could not add 'HBO Go'.Error"
Why???? This Roku 2HD did have HBO GO and both Roku's are in my Roku account.
Did you link it to a different account than the one it was originally linked? I suspect HBO GO was updated and no longer supports the 2XD, which is one of the reasons why you got the notice that it's no longer supported.