Hi John, I think you're likely on the right track looking at EC2 quotas. Assuming you left the "Available instance types" setting in the CloudFormation template at the default value "c5, m5, r5, p3", the "Running On-Demand Standard (A, C, D, H, I, M, R, T, Z) Instances" quota you found is indeed what will limit the number of concurrent instances (measured in terms of vCPUs) that can run out of the c5, m5, and r5 instance type families. (p3 is for GPU computation and has its own quota.) If that quota setting is below 96, you won't be able to start a 96-core instance ([c5,m5,r5].24xlarge types), so your "VCPUCount" -> 96 jobs won't get launched.

You can request a quota increase in the AWS console on the page for that quota (direct link). In my experience AWS processes quota increase requests very quickly, often within minutes - I think the process is partially automated.

Let me know if this doesn't solve your problem.

A single batch job (submitted with RemoteBatchSubmit) runs on a single compute instance, so it's limited to the vCPU count of the largest available instance type. For the c5, r5, and m5 families, this is currently the 24xlarge-size instance types with 96 vCPUs.* To use more vCPUs concurrently, you can submit multiple single batch jobs to run at the same time. If the "Maximum vCPUs" template parameter is >= 192 and your account vCPU limit is high enough, then you can submit two jobs with "VCPUCount" -> 96 and they will run concurrently on two 24xlarge-size instances.

Array batch jobs (submitted with RemoteBatchMapSubmit), on the other hand, can take advantage of multiple running instances simultaneously by splitting a computation into several independent "child" jobs, in a similar manner to how ParallelMap distributes a series of computations across multiple processor cores. We've recently been running some research experiments with array batch jobs using around 900 active cores. Like ParallelMap, RemoteBatchMapSubmit effectively requires you to structure your program as a single, large Map operation.

* The x1 and x1e families support up to 128 vCPUs, but these are specialty instance types with very large amounts of memory and so have a much higher per-vCPU cost than the more general-purpose c5, r5, and m5 families. You can see the full list of instance types (not all of which are usable with AWS Batch) in the Instance Types section of the EC2 console or on the EC2 pricing page.