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That sslchecker test site has been broken for a long time. It is not a good indication of the status of your cert. For example, try this forum's domain community.letsencrypt.org at that site and it will say the cert is faulty. It is not
I did not see a test facility on Digicert's home page that you linked to. Was there some other test site you were concerned about?
The SSL Labs test site is a more thorough test. You can ignore the "CRL IO Error" if you see one. That is a glitch on their site and nothing to do with anyone's cert.
It was an A yesterday I don't think they had it proxied at Cloudflare yesterday but not sure. In fact, pretty sure it wasn't otherwise we wouldn't have seen an LE cert. Cloudflare doesn't use LE by default yet does it?
LE certs are typically issued as the backup certs, but they can be set as primary. The B grade is not surprising, as the Cloudflare defaults strive for increased compatibility. A better score is achievable with some adjustments.
