Uploading SSL Certificate to AWS Elastic Load Balancer

My SSL Certificate on my AWS Elastic Load Balancer is going to expire very soon and I need to replace it with a new one.

I've got the new certificate / bundle / key, uploaded to IAM but it won't show in the drop down in the Load Balancer settings that should let me choose the certificate to apply.

Here is the output when I put aws iam list-server-certificates

To my mind this shows that I have uploaded the new certificate to IAM ok. The top certificate in the list is the one which is due to expire any moment now and the other two are ones I have recently uploaded with the intention of replacing it (They are actually two attempts to upload using the same pem files).

The image below shows that only one certificate is available to choose to apply to the load balancer. Unfortunately it is the one that is about to expire.

The one thing that does strike me as a little odd is that the certificate name in the dropdown - ptdsslcert - is different to the names in the aws iam list-server-certificates output, even though it is the same certificate that expires imminently.

I'm really stuck here and if I don't figure this out soon I'm going to have an expired certificate on my domain so I would be really appreciative of any help on this.