Dear Axe,
Make sure that the web service has been enabled for the Windows AD domain server.
1. Access http://localhost/certsrv/ on the Internet Explorer.
2. Click Download a CA certificate, certificate chain, or CRL.
3. Select the CA certificate you want to export, set the encoding mode to DER, and click Download CA certificate.
4. Click Save to save the CA certificate to a specified directory.
5. Convert the CA certificate format.
The exported CA certificate uses the default format of Windows. You must convert it to the pem format before importing it to the storage system.
6. After the CA certificate is converted, import it to the storage system.
a. Log in to DeviceManager.
b. Choose Settings > Storage Settings > Value-added Service Settings > Credential Management.
c. Import and activate the CA certificate.
More information: https://support.huawei.com/hedex/hdx.do?docid=EDOC1100049969&lang=en
Thanks.