Instance isn't available to select on the provisioning application
This article provides a resolution for the issue where not all the instances are shown in the Organization selector when you provision Omnichannel for Customer Service.
Symptoms
You can't see all the instances from the Organization selector when provisioning Omnichannel for Customer Service.
Cause
For security, reliability, and performance reasons, Omnichannel for Customer Service is separated by geographical locations known as "regions." The provisioning webpage only displays instances in the same region, so you might experience issues where you don't see all the instances from the Organization selector if you have instances in more than one region and provision Omnichannel for Customer Service without selecting the correct region.
Resolution
Go to the Power Platform admin center. Expand Resources, and select Dynamics 365. Select the region in the upper-right corner and select a new region from the dropdown list.
The portal will reload when you change the region. After it has finished reloading, go to Applications > Omnichannel for Customer Service, and then follow the provisioning steps.
The provisioning application you're directed to is associated with the region you chose, and all instances located in that region are displayed as options for provisioning.