Hi @perryraskin,
Welcome back to the Auth0 Community!
In order for the custom domain to help getting around the block of 3rd party cookies on browsers that prevent using them lately, it has to be configured on a subdomain of the application’s website domain. For example, if your application is hosted on example.com , the custom domain would need to be of the format subdomain.example.com .
You can also check out this knowledge article - Chrome Phasing Off Third-Party Support Cookies.
Our documentation on the matter also suggests :
Recent advancements in user privacy controls in browsers adversely impact the user experience by preventing access to third-party cookies. You can use Refresh Token Rotation as an alternative that provides a secure method for using refresh tokens in SPAs while providing end-users with seamless access to resources without the disruption in UX caused by browser privacy technology like ITP.
A large discussion about it was already made under this community post as well - Another post regarding Third-party cookie deprecation in Chrome.
Hope this helps this case, but others as well!
Thanks,
Remus