How To Fix SPRX018 - Error when reading XML document (document contains syntactic errors)

SAP Error Message - Details

• Message type: E = Error

• Message class: SPRX - Proxy Generation

• Message number: 018

• Message text: Error when reading XML document (document contains syntactic errors)

INCLUDE SPRX_GET_WSDL OBJECT DOKU ID TX

What causes this issue?

WSDL document contains syntactical errors, because:
The document is empty
It is a text and not an XML document
It is an XML document, but not a WSDL document
It is an HTML document (for example, an error message)
The XML preamble is missing ( <?xml version="1.0"?> )
For an open tag <xyz> the close tag </xyz> is missing
...

System Response

Proxy generation terminated.

How to fix this error?

There are different explanations as to why no correct document exists:
A "Page Not Found" HTML page was returned instead of a document (the URL
is probably not correct).
A connection to the external server could not be established.
...
If applicable, check the HTTP destination used or the URL in Internet
Explorer.

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

If the source of the WSDL document is the Enterprise Services
Repository:
A "Page Not Found" HTML page was returned instead of a document (the
Enterprise Services Builder address is probably not correct)
The Enterprise Services Builder server is not running at present
The object specified for which a document should be read, does not exist
in the Enterprise Services Builder
The Enterprise Services Builder service that processes the document was
subject to an internal error
Check the connection to the Enterprise Services Repository by using the
following <DS:TX.SPRX_IFR_CONNECTION>checklist</>.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.