Good grief, I just renewed mine and what a pain in the ass. I already had a CORES account from when I upgraded last year. No, not that CORES account. You need a new one, then you link the old one so don't overwrite your account info in your login spreadsheet or you'll need to have it reset for you. None of it is straightforward and now that I've paid, I didn't get a confirmation email or anything, despite them telling you at every turn to provide an email address so you could receive notifications.
The best part is once you've entered your credit card, billing address, etc. the confirmation page looks like something out of a mid 90s site. It actually says "Plastic Card" instead of "Credit Card". Who the hell says that? What an absurd system, that now cost me $35 to support.
Anyway, I hope it's done. I paid and got the confirmation page, just no email and when I look up my callsign the expiration date hasn't moved. It's pending on my credit card, so that's a good sign.
I can't believe the .gov has made a worse system than I could have imagined. The only thing worse is probably the LotW registration. Maybe.