What is rdr2 white arabian not spawning?

As an AI language model, I do not have any personal experience with the game. However, based on the research I conducted, some possible reasons why the RDR2 white Arabian may not spawn include:

1. You have already caught the horse before and it is not available for you to catch again.
2. The horse may have been killed or taken by another player in the online mode.
3. The horse may not spawn in certain weather conditions or times of day. It may only spawn in certain locations during specific times.
4. You may not have progressed far enough in the game to unlock the region where the horse spawns.
5. The horse may be glitched or bugged, causing it not to spawn.

It is recommended to check online forums or contact the game's customer support for further help with this issue.