Issue with Sessions accross Multiple Domains

Hi Guys,

I am currently in the process of setting up a MultiSite environment, relying on the Domain Mapping and Multi-Domain plugins with Single Sign on support.

My intent is to allow users the ability to map their own domain, however access the admin panel using the original URL e.g client1.mainurl.com/wp-admin

If I try to login to any site other than the Network dashboard, after clicking login I am redirected back to the login page. Additionally, when logged in and accessing the frontend, it does not seem like I am logged in (i.e no top bar). I have tried clearing cookies with no success.

It seems as though I have messed up the configuration somewhere, as on the frontend,
"?dm_action=domainmap-check-login-status&domain=EXAMPLE.COM" responds with a 404.

I have granted support access on the WPMUDEV dashboard.

Apologies if this is explained poorly (I am so tired right now) and thanks in advanced for any help with this!!