SSO works on SAPGUI, but not on WebGUI

Hi experts,

I'm using X.509 certificate, I have two Servers, both available on SAPGUI and WebGUI.

But I'm facing some problems.

I can logon using SSO in Server A, both SAPGUI and WebGUI.

I can logon using SSO in Server B, only SAPGUI, but WebGUI still prompts logon page asking for ID and Password.

It seems that my Secure Login Client works well, and the configurations on Server A and B works because I can SSO in SAPGUI.

So what might be the problem that causes my failed to logon to Server B in WebGUI?