Whether a court of appeals must state the basis for denying a certificate of appealability

QUESTION(S) PRESENTED Whether, under this Court's holdings, in Miller-El v. Cockrell, 537 : U.S. 322 (2008), and Buck v. Davis, 580 U.S. 100 (2017), it is inadequate for a Court of Appeals to merely deny an application for Certificate of Appealability, without stating whether the denial is procedural, or on the merits, thereby preventing meaningful review. Especially when the applicant made a substantial showing of the denial of a Constitutional right, by showing as to each issue that reasonable jurists would find : the District Court's ruling debatable or wrong.