SEC_ERROR_OCSP_INVALID_SIGNING_CERT Firefox error
The error roughly translates to “The certificate that you are using to access a website or webpage is invalid or has been invalidated.” The certificate might have been correct at some point, but now it has been invalidated. An apter technical term associated with this process will be OCSP Stapling. Directly quoting the Mozilla Blog: Now we know what is OCSP stapling, coming back to our problem. You are facing this error because the certificate has been revoked or the server you are trying to connect is not recognizing this certificate. This is mostly an issue with some servers and not your computer. The server is not able to handle OCSP stapling properly, and that is why Firefox is throwing an error to you. A temporary but not recommended solution to this problem would be disabling OCSP Stapling on Firefox. This is a temporary solution to access the blocked website, and it should be enabled back for your security. But before you do this, try resetting your Firefox browser and clearing all browser cache before disabling OCSP stapling.
How to disable OCSP Stapling on Firefox
Open up a Firefox window and type about:config in the address bar. Click on I Accept The Risk. Search for the configuration: ssl.enable_ocsp_stapling. Double click on it and set it to ‘false’.
Now try opening the website/webpage that gave you this error. Once you are done browsing, it is recommended to turn on OCSP stapling back again. It ensures better security and protects you from some possible hacks. Another solution to this problem will be, try using another browser. You can use Microsoft Edge or Google Chrome and try opening the same website. This was all in how to fix SEC_ERROR_OCSP_INVALID_SIGNING_CERT on Firefox. I will mention again; this is an error due to some invalid/invalidated certificates or bad servers. It is recommended not to turn off OCSP Stapling, but if you want to access the website, you can temporarily do so.
