iOS13/14 DEP enrollment failure with Xcode error "cannot accept the authentication method NSURLAuthenticationMethodClientCertificate"

We have some new iOS DEP/ABM devices(iOS/iPadOS 14) but failed to enrol to MDM server.

Find below errors in Xcode log when activate the DEP device during SSL connection setup:
______Jan 12 15:28:42 iPad Setup(CFNetwork)[329] <Notice>: Connection 16: asked for TLS Client Certificates
Jan 12 15:28:42 iPad Setup(CFNetwork)[329] <Notice>: Connection 16: issuing challenge for client certificates, DNs(0)
Jan 12 15:28:42 iPad Setup(CFNetwork)[329] <Notice>: Connection 16: asked for TLS Client Certificates
Jan 12 15:28:42 iPad Setup(ManagedConfiguration)[329] <Error>: <MCHTTPRequestor: 0x280360030> cannot accept the authentication method NSURLAuthenticationMethodClientCertificate______

This error results in no Certificate finish to gateway, then gateway sends Close notify to Client and then connection reset.

Previously enrolled iOS devices and non-DEP devices work well.

You can find the Xcode logs for a DEP device and a non-DEP device.

Since issue happens at the beginning of activating the DEP devices and customer failed to get the sysdiagnose log when device is at this phase. Appreciated if anybody can share some other idea to get the sysdiagnose log.

We have Feedback ticket FB9045594 created for this issue and attached Xcode logs there, thank you!

Thanks,
Wei