Forza Horizon 2 not online available

This pre order bonus just unlock Audi RS4 (but Audi RS4 is available in Forza Horizon 2).

And this pre order bonus is available in Microsoft stores not online stores.

Hi SquallLion1

Unfortunately Forza Horizon 2 - Storm Island has reached "end of life" status and was removed from Xbox store on September 30th 2018

Here is an extract form the Forza Week in Review post on https://www.forzamotorsport.net

"Forza Horizon 2

A heads up for the Forza community: Forza Horizon 2 will reach “end of life” status on September 30. That means that the game and its associated DLC will no longer be available for purchase. After September 30, players who own Forza Horizon 2 will still
able to download and play the game and its associated content as normal. However, Forza Horizon 2 and its DLC will no longer be for sale. Forza Horizon 2 is currently available as part of August Games With Gold so, if you haven’t played it already, now is
a great time to grab it."

Yes you can still play it online. Just keep in mind in the future that issues related to game servers are in-game issues addressed by the game developer, in this case Turn 10. I suggest you to post directly and FH support forums in the future.

yip servers are still up for it

They removed the online capabilities when Forza 4 came out. You can no longer play online on Forza 2

It reached end of life status around that time so it's no longer available to purchase digitally, but it's servers are still up.