Microsoft has deprecated the WS-Trust authentication type security protocol, and hence connecting via username and password is not possible for D365 CE tenants any longer.
We recommend you to work with Entra ID impersonation for your D365 CE connection (see Configuring the dox42 app registration in Entra ID). However in some scenarios, for example when using Microsoft Power Automate or PowerApps (see also Generating D365 CE or Dynamics CRM Documents from Flows and Power Apps), the connection via an Entra ID application user, as well as a client secret or certificate is needed.
You will still need to follow the instructions on Registering the dox42 app in Entra ID.
Steps
Register the dox42 app in Entra ID.
Upload your certificate and/or have your client secret for your Entra ID app ready.
Add an Entra ID application user to your D365 CE environment.