Why did the SSL expire? I'm only asking because I have a domain that also uses a certificate from Let's Encrypt / R3 / ISRG Root X1 and I've never had to renew

Why did the SSL expire? I'm only asking because I have a domain that also uses a certificate from Let's Encrypt / R3 / ISRG Root X1 and I've never had to renew it. (It seems like they auto-renew every 90 days?)