SSH Agent forwarding does not work

[xl32]

I have Pageant on Windows host, that works fine with PuTTY on workstation A. When I connect using SSH2, it works with ssh 2 client on Linux host B connecting to Linux host C.
I clearly see that $SSH_AUTH_SOCK is exposed on host B:

b.example.com $ echo $SSH_AUTH_SOCK
/tmp/ssh-XXXXekFLue/agent.3841213

when I'm trying to connect to Linux host C from B, ssh3 -v user@c.example.com/ssh3-term I see 5:50PM ERR could not dial c.example.com:444/ssh3-term: no suitable identity found.

At the same time ssh2 ssh user@c.example.com connects as expected.

Please advise.