ALB DNS could not be resolved after account re-activation

Hello.

Please try name resolution using the "nslookup" command instead of pinging the ALB.

nslookup ALB-DNS-NAME

If the ALB public IP address cannot be resolved using the above command, there may be a problem with your AWS account, so we recommend that you open a case with AWS Support under "Account and billing".
https://docs.aws.amazon.com/awssupport/latest/user/case-management.html

When your account was reactivated were all the resources back in place, such that everything matches what was deployed in the account before suspension?

In the AWS Console select the region that the load balancer is in, then go to EC2 and in the left hand pane choose Load Balancers.

Is the load balancer listed there, and if it is then verify that its DNS name and IP address is what you expect.

Also, if you are trying to access the load balancer using a Route 53 Alias or CNAME (instead of the plain myloadbalancer-123456789.[region].elb.amazonaws.com type of name)? If you're using an alias then check it's still valid.