Hi Luke Rosser,
Welcome to the Microsoft Q&A Platform! Thank you for asking your question here.
I understand the challenges you're facing with capacity issues in the South Central US region.
When using the "Start VM on connect" feature in Azure Virtual Desktop, the system attempts to start the VM associated with the user's session. If the VM fails to launch due to capacity issues, Azure Virtual Desktop will try to start another VM within the host pool. It does not stick to the failing VM. instead, it will move on to another available VM in the pool.
Using different VM SKUs can help improve the chances of finding available capacity.
Refer to the documentation.
Azure Virtual Desktop Start VM Connect FAQ - Azure | Microsoft Learn
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