How to use old Cookie with new User-agent

Presumably the new browser doesn't share the same cookie as the original session and therefore cookie persistence doesn't work. You could try to find a way to inject this cookie into the new browser session, share the cookie repository or use permanent cookies to see if that helps. You can use universal persistence if there is something that links the two sessions such as a session ID. If this is just a completely new session accessed via another browser then i don't see that there is much you can do except for use source address persistence.