FamilySearch.org accounts are now separate from ChurchofJesusChrist.org accounts.
Previously, any account created on FamilySearch.org created a matching account on ChurchofJesusChrist.org. Similarly, any account created on ChurchofJesusChrist.org created a matching FamilySearch account.
Beginning September 13, 2021, FamilySearch accounts are created and managed only on FamilySearch.org and Church Accounts are created and managed only on ChurchofJesusChrist.org.
If you have an account on ChurchofJesusChrist.org, you can continue to use it to log in to FamilySearch.org. When you go to the Sign In page on FamilySearch.org, select the Sign In with Church Account button. That way, you won’t have to keep track of two separate usernames and passwords.
Separating these accounts allows FamilySearch.org to accommodate future growth, simplify access, improve security and privacy, and conserve Church resources.
From the article “FamilySearch and Church Account Split”