I'm using Librewolf, which is a fork of Firefox, and am updated to the latest version (136.0.1-1) and I was able to access this site this morning without any issues. I just finished a Windows update (Windows 11, version 24H2) which seemed to go fine, but now when I try to access Manga Updates using Librewolf I get the following error:

Secure Connection Failed

An error occurred during a connection to www.mangaupdates.com. The OCSP server suggests trying again later.

Error code: SEC_ERROR_OCSP_TRY_SERVER_LATER

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.

Please contact the website owners to inform them of this problem.

I've tried reaching the site in Chrome and don't have any issues. Not sure if this is happening in the standard Firefox browser, but hopefully this is something that can be easily fixed.

It's back to working properly now. Not sure if this was something you fixed or your end or it just naturally sorted itself out, but we're all good!