Actual availability of instance type in region

There's no document that shows actual instance availability for region as it's a pretty dynamic number. SageMaker is backed by EC2 instances for training jobs and when you receive that error it just means there isn't currently existing EC2 capacity for your specific use case. Here's a document on troubleshooting that specific error. You'll notice that the first troubleshooting is just waiting a few minutes then try again. That's generally because we don't always have large instance types just running idle, so once you receive that error, if you wait a few minutes, AWS works on spinning up capacity to meet your need. Sorry for the inconvenience, but I'd try those steps before moving region, as you may experience the same error in other regions as well.