Merge PDFs -BadRequest

Using Power Automate Desktop to test PDF Merge.   The inbuild action - "Merge PDF Files" works correctly with my 2 sample pdf files but the Adobe PDF Services action - "Merge PDFs" constantly fails with the error - Cloud connector call failed with status code 'BadRequest'.  complete message details below.

I am using the same files as the working inbuilt action.  Also tested with other pdf files.  Connector is showing as "green". Also have created new connectors but that has made no difference.  Does not work whether I pass the file name in a parameter or add them in individually.

Correlation Id: b91d6aad-457b-4989-94be-5915d1231241

Additional info:
{
"StatusCode": "400",
"Message": "",
"Body": {
"error": {
"code": "invalidFileContent",
"message": "Invalid file content"
}
},
"Headers": {
"Pragma": "no-cache",
"Transfer-Encoding": "chunked",
"Vary": "accept-encoding",
"Strict-Transport-Security": "max-age=31536000; includeSubDomains",
"x-ms-islandgateway": "_prdil102sukgb0_4",
"x-ms-ppapigateway": "gb000001U",
"x-ms-gateway-clusters": "prdil102suk",
"mise-correlation-id": "2e6a81c0-eb67-49b7-bb7d-a87ad93e74c9",
"X-Request-ID": "1Y2ETCW55EvKnJuwEWQSoQGoTo5j9jDK",
"X-Content-Type-Options": "nosniff",
"x-robots-tag": "noindex,nofollow",
"x-ms-environment-id": "default-8d733bf0-442e-4449-b747-a765ea359ff8",
"x-ms-tenant-id": "8d733bf0-442e-4449-b747-a765ea359ff8",
"x-ms-dlp-re": "-|-",
"x-ms-dlp-gu": "-|-",
"x-ms-dlp-ef": "-|-/-|-|-",
"x-ms-mip-sl": "-|-|-|-",
"timing-allow-origin": "*",
"x-ms-apihub-cached-response": "false",
"x-ms-apihub-obo": "false",
"x-ms-failure-cause": "Apim",
"x-ms-request-id": "uksouth:51dc7806-5b41-4726-88ef-9f8d3a50314b",
"x-ms-correlation-request-id": "b91d6aad-457b-4989-94be-5915d1231241",
"x-ms-correlation-id": "b91d6aad-457b-4989-94be-5915d1231241",
"x-ms-flow-mobile-ios-version": "1.3.0",
"x-ms-flow-routing-request-id": "UKSOUTH:20250703T105826Z:51dc7806-5b41-4726-88ef-9f8d3a50314b",
"x-servicefabric": "NoRetry",
"x-ms-service-request-id": "ce0587c6-6f0a-4096-8b1d-3253d7c6b6d6",
"x-ms-activity-vector": "00.01.00",
"Server-Timing": "x-ms-igw-upstream-headers;dur=392.9,x-ms-igw-req-overhead;dur=1.1",
"Cache-Control": "no-store, must-revalidate, no-cache",
"Date": "Thu, 03 Jul 2025 10:58:25 GMT"
}
}