I'm receiving this error DLG_FLAGS_SEC_CERT_DATE_INVALID on my site which has an SSL certificate that is valid on the portal to March 7, 2019. On March 7, 2018 I started receiving the error.
ok I solved it. Even though I have auto renewal on in the portal, you
still have to rebind the new ssl certificate in the app service because
azure when they renew the certificate they don't update the original but
issue a new one. It's these little things that forget to get mentioned.