EDIT: Solved. Switching locations on AWS, then creating a new BatchComputeEnvironment, solved the issue.
Following the workflow https://reference.wolfram.com/language/workflow/SetUpTheAWSBatchComputationProvider.html, I have a working BatchComputeEnvironment, and have authenticated the AWS service connection using my local credentials files. But when I run a RemoteBatchSubmit command of the form
RemoteBatchSubmit[RemoteBatchSubmissionEnvironment["AWSBatch", <|"JobQueue" -> "...",
"JobDefinition" -> "...", "IOBucket" -> "..."|>], 2 + 2]
, it gives the error:
RemoteBatchSubmit::awsbatch-missingdefinition: The specified job definition arn:aws:batch:us-east-1:[...] does not exist.
Other AWS calling functionality is working fine, such as:
ServiceConnect["AWS"]["GetService",
"Name" -> "Translate"]["TranslateText", "Text" -> "今日は良い一日だった",
"SourceLanguageCode" -> "auto", "TargetLanguageCode" -> "en"]
I've triple-checked the details are correct, and match what AWS shows me and what the workflow told me to do. And I can even submit jobs manually using the same job definition at console.aws.amazon.com/batch. Hence I have no clue about the error. Essentially, Mathematica is failing to recognise the existence of a job definition which exists. Any ideas?