Hello Naman Parekh,
We checked the conditions given in the documentation, when certificate status shows FAILED_NOT_VISIBLE. Looks like all the required conditions are met, but still we face this issue.
1. Updated the DNS records with the load balancer IP address.
Result from finding the IP.

2. SSL certificate is attached to the load balancer proxy, and added a forwarding rule to port 443.
Even after reading a few articles on stack-overflow / some other articles, we couldn't find the exact reason why it is happening this way. Previously it used to work properly, but in recent times, we are getting error from certificate.
Please let us know if we are missing out on something.
Thank you.