Versions I am using -

zeep==3.4.0
lxml==4.7.1
xmlsec==1.3.8
libxml2 = 2.9.2

Centos75
python 3.8.10

Error detail:

service_1            | Traceback (most recent call last):
    service_1            |   File "/app/wf_iccp/endpoints/home.py", line 59, in get_data_source_request
    service_1            |     return get_service(auth_cert=crt, auth_key=key).GetDataSource()
    service_1            |   File "/pyenv/versions/wf-iccp/lib/python3.8/site-packages/zeep/proxy.py", line 40, in __call__
    service_1            |     return self._proxy._binding.send(
    service_1            |   File "/pyenv/versions/wf-iccp/lib/python3.8/site-packages/zeep/wsdl/bindings/soap.py", line 118, in send
    service_1            |     envelope, http_headers = self._create(
    service_1            |   File "/pyenv/versions/wf-iccp/lib/python3.8/site-packages/zeep/wsdl/bindings/soap.py", line 95, in _create
    service_1            |     envelope, http_headers = client.wsse.apply(envelope, http_headers)
    service_1            |   File "/pyenv/versions/wf-iccp/lib/python3.8/site-packages/zeep/wsse/signature.py", line 104, in apply
    service_1            |     _sign_envelope_with_key_binary(
    service_1            |   File "/pyenv/versions/wf-iccp/lib/python3.8/site-packages/zeep/wsse/signature.py", line 287, in _sign_envelope_with_key_binary
    service_1            |     bintok.text = x509_data.find(QName(ns.DS, "X509Certificate")).text
    service_1            | AttributeError: 'NoneType' object has no attribute 'text'

QName prints - and ns.DS below refers to constant

 print(QName(ns.DS, "X509Certificate"))

{http://www.w3.org/2000/09/xmldsig#}X509Certificate

xml certificate(I dumped the x509_data) and seems to be there.

<X509Data xmlns="http://www.w3.org/2000/09/xmldsig#" xmlns:wsse="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd" xmlns:soap-env="http://schemas.xmlsoap.org/soap/envelope/" xmlns:ser1="http://mastercard.com/sd/pc/service" xmlns:ser="http://mastercard.com/sd/pc2/service">
        <X509Certificate>
            CERTIFICATEVALUE
        </X509Certificate>
        <X509IssuerSerial>
        <X509IssuerName>IUSSER_DETAILS</X509IssuerName>
        <X509SerialNumber>SERIALNUMBER</X509SerialNumber>
        </X509IssuerSerial>
    </X509Data>

It was working before. Not sure what's going on . I tried using different versions of lxml but no luck. Any advice?

Thank you so much!!