Below is what happens when your account is downgraded from a paid plan to free.
Personal plan
If you have more than one profile, all but one will be disabled and unavailable until you upgrade again.
If you had a subdomain or custom domain, it will no longer work. You'll have to use the link with your username (i.e. https://campsite.bio/myusername).
If you had a background image or pattern, it will go back to a flat color.
Your uploaded images are no longer available and aren't on your links anymore. If you decide to upgrade again you can get your uploaded images back.
Any opt-in form, group, feed or form link has been archived.
If you have any carousels links, all but one will be archived if any have a single banner.
Any other Pro features will be disabled.
Organization plan
All profiles in an organization will no longer be available after an organization is dowgraded to the free plan.