Renewing AppleCare for MacBook Pro

For some background - I bought my MacBook Pro in 2017 and at the time of purchase, I also bought 3 years of AppleCare. It recently expired because I forgot to renew it, and when I talked to an agent on the phone, she told me I can't renew the AppleCare for my Mac once it's expired. Everything I've read online indicates that I should be able to buy a new protection plan though, so I'm confused.

So my question is, am I able to renew coverage for my MacBook? It seems weird to me that I wouldn't be able to renew or buy coverage for it at all once it's expired.