ACM requesting Cert

This article might help you

https://repost.aws/knowledge-center/acm-email-validation-custom

Hi,

You could check validation type, is DNS or email?

Usually DNS is automatic and, if configures correctly, should take from a few minutes to a day depending on propagation.

Email validation is manual and if you don’t approve the link within 3 days from the sending, then you have to request again as expired.

https://docs.aws.amazon.com/acm/latest/userguide/certificate-validation.html

If above guide doesn’t help, you may worth to contact Support, hope it helps.