I have modified the config to enable:

Networking --->
Networking options --->
Transformation user configuration interface [CONFIG_XFRM_USER]
PF_KEY sockets [CONFIG_NET_KEY]
TCP/IP networking [CONFIG_INET]
IP: advanced router [CONFIG_IP_ADVANCED_ROUTER]
IP: policy routing [CONFIG_IP_MULTIPLE_TABLES]
IP: AH transformation [CONFIG_INET_AH]
IP: ESP transformation [CONFIG_INET_ESP]
IP: IPComp transformation [CONFIG_INET_IPCOMP]
IP: IPsec transport mode [CONFIG_INET_XFRM_MODE_TRANSPORT]
IP: IPsec tunnel mode [CONFIG_INET_XFRM_MODE_TUNNEL]
IP: IPsec BEET mode [CONFIG_INET_XFRM_MODE_BEET]
The IPv6 protocol ---> [CONFIG_IPV6]
IPv6: AH transformation [CONFIG_INET6_AH]
IPv6: ESP transformation [CONFIG_INET6_ESP]
IPv6: IPComp transformation [CONFIG_INET6_IPCOMP]
IPv6: IPsec transport mode [CONFIG_INET6_XFRM_MODE_TRANSPORT]
IPv6: IPsec tunnel mode [CONFIG_INET6_XFRM_MODE_TUNNEL]
IPv6: IPsec BEET mode [CONFIG_INET6_XFRM_MODE_BEET]
IPv6: Multiple Routing Tables [CONFIG_IPV6_MULTIPLE_TABLES]
Network packet filtering framework (Netfilter) ---> [CONFIG_NETFILTER]
Core Netfilter Configuration --->
Netfilter Xtables support [CONFIG_NETFILTER_XTABLES]
IPsec "policy" match support [CONFIG_NETFILTER_XT_MATCH_POLICY]
Cryptographic API
Select algorithms you want to use...
Encrypted Chain IV Generator [CRYPTO_ECHAINIV]

Why did I still get the error?

Thanks