This is probably more an operational issue than a bug.
Let’s Encrypt appears to have performed a mass revocation of a subset of their certificates; certificates for forum.wolfery.com, and mucklet.com appear to have been affected. I am only able to send this by virtue of the --ignore-certificate-errors argument to Chrome, which allows me to bypass it. Without the argument, I get either ERR_FAILED from Chrome and edge, or an out of date cached copy of the page; a shift-reload yields NET::ERR_CERT_REVOKED.
Strange. Opera GX doesn’t seem to mind, and even tells me that there’s a valid cert, only saying that it’s now out of date by clicking on it to have a closer look. Whereas Firefox seems to require the same type of workaround as Chrome.
New certificates has been issued, so the problems should be resolved.
@Xetem, one reason why it still worked in some browsers is because the browser in itself keeps a list of trusted root certificates. I don’t know these things well enough, but I believe your browser must update this list before the revocation takes effect.