To narrow down the cause, you can start with confirming whether the service is accessible from:
-Pod IP
-ClusterIP of the service, inside the cluster
-and then test the load balancer.
You can also test the connectivity from a curl command ideally from a host machine inside the same vnet where the AKS is created.
For example, "curl EXTERNAL-IP:8080"
They you would need to look at allowing traffic access from the internet in the NSG applied to the vnet/subnet for aks.
Let me know your observations and I can help troubleshoot further.