Need to migrate Authentication method from default to SAML

We are using LTS 9.9 Developer Edition. We have configured SAML Authentication Properly but after that we get this below message while we use Login with SAML option.

You’re not authorized to access this page. Please contact the administrator.

Reason: This account is already associated with another authentication method. Sign in using the current authentication method, or contact your administrator to transfer your account to a different authentication method.

we have followed this Migrating SonarQube Users Between Identity Providers (with a focus on LDAP → SAML) but negative.

What did you try? What didn’t work? Please be as specific as possible.