The cert of nap.bg and the recent bulgarian tax SNAFU

Since 2019-07-15 there is a major SNAFU in the BG tax authorities. World and dog tax information and ID leaked on the interwebz. I have sporadic SSL failures connecting to https://nap.bg with firefox, lynx and openssl s_client. e.g: $ openssl s_client -connect nap.bg:443 Verify return code: 21 (unable to verify the first certificate) On the other hand, ssllabs.com claims the Cert is OK, grade B. Is the cert of nap.bg OK?