I'm getting a NET::ERR_CERT_COMMON_NAME_INVALID error when trying to open the link to redeem my free course for entering in the jam. Anyone else experienced this?

I have not, and that error is concerning. It's one that a browser will throw when the SSL certificate domain does not match the domain name you're visiting (IE: cert says google.com, but the domain is giggle.com). Which doesn't make sense. Sounds like your network might not be secure. Are you using any proxy services by chance? Or are you connected to a public network?

Forgot to update; it works on my phone. That makes it slightly more troublesome, with all the links required, but it'll do. Now that you mention it, I think there might be some always-on VPN running on my work laptop that was probably the culprit.