I am trying to login user (not member) in custom Controller. It does not login user to backoffice.

if (ModelState.IsValid && Membership.ValidateUser(model.Username, model.Password))
{
  FormsAuthentication.SetAuthCookie(model.Username, model.RememberMe);
}

I have changed web.config to use UsersMembershipProvider by defualt

<membership defaultProvider="UsersMembershipProvider" userIsOnlineTimeWindow="15">
      <providers>
        <clear />
        <add name="UmbracoMembershipProvider" type="Umbraco.Web.Security.Providers.MembersMembershipProvider, Umbraco" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="10" useLegacyEncoding="false" enablePasswordRetrieval="false" enablePasswordReset="false" requiresQuestionAndAnswer="false" defaultMemberTypeAlias="Member" passwordFormat="Hashed" allowManuallyChangingPassword="false" />
        <add name="UsersMembershipProvider" type="Umbraco.Web.Security.Providers.UsersMembershipProvider, Umbraco" minRequiredNonalphanumericCharacters="0" minRequiredPasswordLength="6" useLegacyEncoding="false" enablePasswordRetrieval="false" enablePasswordReset="false" requiresQuestionAndAnswer="false" defaultMemberTypeAlias="Member" passwordFormat="Hashed" allowManuallyChangingPassword="false" />
      </providers>
    </membership>

It is linked to this issue https://our.umbraco.org/forum/using-umbraco-and-getting-started/91172-cant-login-user-in-custom-login-controller

I have also tried adding Members.Login(model.Username, model.Password); but it returns false

And I am getting yourAuthCookie as response.