"code": "BatchZipMustContainOneFileError",
	"target": "Unknown",
	"details": [
			"code": "BatchZipMustContainOneFileError",
			"number": 201,
			"message": "Compressed archive did not contain one file.",
			"description": "The compressed archive file -0- did not contain exactly one file when uncompressed.",
			"faultCode": "Client",
			"helpLink": "",
			"severity": "Error"

This indicates that the compressed archive did not contain exactly one file. AvaTax processes one file per batch. You can only upload one file per batch, even if that file is a compressed ZIP. The ZIP must decompress to exactly one file.

If you want to upload more than one file, please upload more than one batch.