Hello @Joshua Hui , Thanks for using Microsoft Q&A Platform.
As we know the preview API is currently available in three regions :West Europe, West US2, East US: https://learn.microsoft.com/en-us/azure/applied-ai-services/form-recognizer/whats-new?view=form-recog-3.0.0&tabs=csharp#march-2023
I just reproduced the East US region for both the layout and general model, and I was able to select the preview API.
Could you please check the region details again, as well as try regenerating the keys in the Azure portal for your resource and then check in the FR studio to see if that helps?
I hope this helps.
Regards,
Vasavi
-Please kindly accept the answer and vote 'yes' if you feel helpful to support the community, thanks.