I have recently deployed my website to domain.com - and I am attempting to set the cookie from a response header from a request to api.domain.com.

Reading here Share cookie between subdomain and domain - it seemed simple that I just had to add the Domain to my set cookie that is being sent from api.domain.com

My set cookie header now looks like set-cookie: token=${token}; HttpOnly; Max-Age=5184000; Path=/; Domain=domain.com

But it is still not setting the token - or any header I try with the domain included

I've been trying to debug for a few hours but cannot see where I'm going wrong - though I didn't expect them to effect the setting of the cookie, I tried removing HttpOnly, Max-Age & Path

I've also tried setting the domain to Domain=.domain.com