Issue posting XML Call

I'm having issues using system.net.httpPost using an XML string. I have verified my string works when copied and pasted into Insomnia, so syntax is not an issue. The return code gives me the following:

Action 'Transform XML using XSLT-<Custom parameter>' did not complete. Details: Data at the root level is invalid. Line 1, position 1.

I have not been able to get anything other than this error, even when attempting to put the most basic xml data. For example, this gives me the same data.

testNoData = """<?xml version="1.0" encoding="utf-8"?>"""
returnInfo = system.net.httpPost(url=hostUrl,contentType = 'text/xml',postParams=testNoData)	

Has anyone run into this error before? I've searched around extensively and it generally seems to be a potential hidden character or string type issue. Thanks for any help.

postParams isn't the name of the parameter you're looking for, it's postData.

Also - obligatory reccomendation that you should be using system.net.httpClient instead.

Oh my goodness, thanks. I have only used json up to now. And I will switch to the client method instead.