MP Reg: Failed to get client(GUID:) public key: 0x80040238
0x80040238 simply means the public key is not found. This error will almost always be reported when a new client is trying to register itself. Because the client is new, it is normal that no public key exists in the ClientKeyData table for that client. It is after that error is reported that the registration happens.
For example, here is a MP_RegistrationManager.log displaying successful registration where verbose agent logging has been enabled on the SCCM site server:
We can see the 0x80040238 error is just informational, as long as a second “Confirmation” of “ClientRegistrationResponse” can be received by the client. Here’s what the client’s ClientIDManagerStartup.log says at the same time: