Change Password XAPI call not working, XAPI Service in BP fails with ErrorCode="YCP0084

XAPI service in BP fails with:
ErrorCode="YCP0084
ErrorDescription="Invalid User identifiers passed"

From BP:
<operation name="XAPIServiceType">
<participant name="XAPIService"/>
<output message="XAPIServiceTypeInputMessage">
<assign to="api">changePassword</assign>
<assign to="xml">
<User Id="abctest1" NewPassword="password1"
Password="testpass" />
</assign>

The error posted was due to invalid attributes of Id and NewPassword in your XAPI service was used.

There are 4 attributes that are available within the changePassword XAPI, which are:
ExistingPassword, Loginid, Password, and UserKey.

In SI, there is a xapidocs folder which contains all the available documentation on XAPI.

To get here, go to the SI base install directory, and see a folder called xapidocs. This contains a folder called api_javadocs which contains an html file structure with all valid api calls including schemas.

Copy the xapidocs folder (and all of the subfolders) to a location accessible to your browser and then open xapidocs/index.html in a browser, and this will list all available XAPIs including 'changePassword'.

Within the 'changePassword' XAPI, it only list 4 attributes that are available under the User element, and the attributes are: ExistingPassword, Loginid, Password, and UserKey.

Also Under 'Validation Condition' is specifies: If Invalid User Identifiers - Loginid or UserKey are passed.
You will receive error: YCP0084 Invalid User identifiers passed.

Use valid attributes within the 'changePassword' XAPI. The 4 attributes that are available under the User element are: ExistingPassword, Loginid, Password, and UserKey.