Can't play the Arena with friend

[FuYu]

So, the arena isn't working. I invite my friend to play with me, and start creating the game. But launch always fails, is there anyway to fix it?

 

[NCSGeek]

So, the arena isn't working. I invite my friend to play with me, and start creating the game. But launch always fails, is there anyway to fix it?

Could be two things. Either you are not setup for multiplayer in general, or you are not using the Beta.

Here is a tutorial on how to setup multiplayer

And to enable the Beta Update option (which is required for Sparta as of now), head to the celeste launcher and click on the hammer icon. Then click Game Scan, then enable the Beta Update option. Run a game scan after enabling it to "apply" the choice.