How to use certificate?

[alex1983]

Hi to all,
I'm trying to IPXE using a HTTPS server. I have a problem with certificates:
I have created CA-ROOT certificate,
I have created the CA-SUB-ROOT certificate,
and I've signed the server certificate with the CA-SUB-ROOT.
Finally I insert the client certificate and its private key in the iPXE iso.

When I start the iPXE boot, I receive the following message:
TLS 0x103ae4 certificate validation succeeded
TLS 0x103ae4 received fatal alert 48
Operation not permitted (http://ipxe.org/410de13c)

Which is my error?
if I launch certstat, I can see that all certificate are validated but client. Client certificate is only embedded and not validated, why? Client and server certificate are both signed with the same CA but server is validated and client not.

Thanks in advance for the response.