Members only site – still need the lost password page accessible

I believe your if statement is incorrect it should be an AND (&&) not OR

so try

if ( ! is_user_logged_in() && ! is_page( 'lost-password' ) ) {

EDIT

Try using $object = get_queried_object() for checking the post slug

$object = get_queried_object();
if ( ! is_user_logged_in() && ( ! $object || 'my-account' !== $object->post_name ) ) {
  // ...

EDIT 2 The page slug was wrong so updated in the second example