Domain error for 'www' version of domain.

Hi for some reason I am getting an error for my domain https://www.pairmeup.io/ ( not secure) - while without the www. everything works.
In plasmic under deployment it shows me that everything is set up correctly. It also worked in the past, so I dont know when this issue started. I checked the dns records and for www I have:

CNAME www cname.plasmicdev.com

Now I wanted to find any documentation on how to set up your own custom domain with plasmic to check if i am missing any records but I can no longer find the documentation. Has it moved?

I also have a link to the plasmic project
https://studio.plasmic.app/projects/tKXQ9HozoLTizzT9NzHJsq

EDIT: Now under custom domain I removed the domain to readd it and get an error:
pairmeup.io: DomainUsedElsewhereInVercel

Okay solved - I added www.pairmeup.io to vercel under setting and redirect pairmeup.io to www. Thank you!