Invalid OCSP signing certificate in OCSP response. Error code: sec_error_ocsp_invalid_signing_cert

It looks like a security feature on Firefox somehow stops you from getting into your Sharepoint. OCSP is actually an advanced security feature in Mozzila Firefox that checks on the website’s certificate. In this case, there’s probably an issue on O365.
ocsp

However, if you are already starting to crack your head or pulling your hairs, there’s always a quick workaround you can use. To work around this issue, you will need to turn off the OCSP Stapling function in your Firefox.

firefoxaboutconfig

Enter about:config into the Firefox address bar

firefoxvoidwarranty

You will be presented with this warning. Go ahead, click on I accept the risk!

searchocsp

Search for “OCSP” and preference will be filtered down to those related to OCSP

ocspstaplingfalse

Double click the one that sales security.ssl.enable_ocsp_stapling and make sure the value is “false” . VOILA!! Your Sharepoint should start working again !

This settings, however, will slightly lower your security. You might want to come back here and revert the settings once the issue has been resolved on O365.

Cheers~

 

 

 

You can’t use the domain because it’s not an accepted domain for Exchange System yet

Been getting cases about domains not accepted on Office 365. Error would go like “You can’t use the domain because it’s not an accepted domain for Exchange System yet”

Based on my experience, it may take 72 hours to take effect after verifying custom domain and adding DNS records in Office 365. So I usually would suggest to wait it out for at least 24 hours to see if the issue resolves by its own. Usually it does, unless there’s a bug somewhere on the portal.

What you can do to troubleshoot.

1. Go to Exchange Admin Center
2. Select Mail Flow > Accepted Domains
3. Make sure both yourdomain.com and yourdomain.onmicrosoft.com have this “Domain Type=Authoritative”, with yourdomain.com set as default domain
4. If you have access via Exchange Online Powershell, you can try running Get-AcceptedDomain to see if your domain is listed there.