Hey @Enrico Parisi I don't have access to a regular terminal, but I tried doing that using a web terminal provided by InterSystems online course, it's working fine. I am getting the complete bundle.
Can you tell what is the issue? Why am I not able to get the same through my CSP page?

I am using studio's terminal to run the code.

set ccdaStream = ##class(%Stream.FileBinary).%OpenId("/tmp/CCDA_CCD_b1_Ambulatory_v2.xml")

write "Size of CCDA Stream: ", ccdaStream.Size,!
Size of CCDA Stream: 171823
set xsltTransform = "SDA3/CCDA-to-SDA.xsl"
set tTransformer = ##class(HS.Util.XSLTTransformer).%New()

set tSC = tTransformer.Transform(ccdaStream, xsltTransform, .sdaStream)

if 'tSC write "Transformation to SDA3 failed with error ",$system.Status.GetErrorText(tSC),!

set fhirStream = ##class(%Stream.TmpBinary).%New()

set SDA3ToFHIRObject = ##class(HS.FHIR.DTL.Util.API.Transform.SDA3ToFHIR).TransformStream(sdaStream, "HS.SDA3.Container", "R4")

if '$isobject(SDA3ToFHIRObject.bundle) write "Failed to transform SDA3 to FHIR",!

do SDA3ToFHIRObject.bundle.%ToJSON()
{"resourceType":"Bundle","type":"transaction","entry":[]}

Yes, I tried the exact code just instead of "c:\temp\CCDA_CCD_b1_Ambulatory_v2.xml" I gave the location of same CCDA on my server.
Yes, it is IRIS for Health.