AWS Lightsail SSL Certificate won't validate

Question

I have a Lightsail distribution and now I want to add a certificate for SSL. I created the certificate using my_site.com and www.my_site.com and it then gave me two CNAME records to add to my DNS for verification.

I'm using AWS Route53 for DNS and not the Lightsail DNS. So I went to Route53 and added the 2 CNAME records, name and value, to the DNS zone. All good.

But when I go back to the Lightsail certificate section, it shows that it's still validating. I've waiting some time, but no luck.

This is a pretty simple operation which is why I'm wondering how it could stall/fail. The site (and Route53 DNS) was working before trying to add the distribution and certificate.