I agree with Robert. Have you double checked this.
If you have double checked the regions but still getting an error, customer care will be able to help get this fixed. They will need network har logs specifically looking at the SAML request so please provide this information as it will help the customer care team in their investigation.
If you need guidance opening a ticket with care we have these helpful docs!
Login in to "My Support Portal" links:
Core and Satellite AWS regions:
Please note that you must be a designated contact for the org to contact GC Customer Care.
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Cameron Tomlin
Genesys - Employees
Online Community Manager/Moderator
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