Target group greyed out / not selectable when configuring listener rule on new ALB, despite matching VPC, subnet, and protocol

Question

I'm setting up a new Application Load Balancer (region: ap-south-1) to consolidate 3 existing ECS Fargate services — previously behind 3 separate ALBs — using host-based routing on a single shared ALB.

Setup:

3 target groups already exist, target type IP, protocol HTTP:443, protocol version HTTP1
All 3 target groups are currently attached to another working ALB in the same account/region, functioning correctly
New ALB is Internet-facing, IPv4, same VPC as the target groups
2 Availability Zones selected, using the same public subnets as the existing working ALB

Issue:
When trying to select a target group in the listener's default action ("Forward to target group") or in a listener rule, the target group appears in the dropdown list but is greyed out / not selectable, even though it works fine attached to another ALB with identical VPC/subnet/protocol configuration.

Things I've already verified/tried:

VPC of target group matches VPC selected for new ALB
Subnets match an already-working ALB's subnets exactly
Target group protocol (HTTP:443) is ALB-compatible
IAM user has ElasticLoadBalancingFullAccess
Tried multiple browsers (Brave, Firefox)
Hard refresh, browser zoom reset to 100%
Tried keyboard navigation (typing target group name + Enter) instead of mouse click
Tried creating the ALB first with a "Return fixed response" default action, then attaching the target group afterward via Listener → Rules — same greyed-out behavior there too

Has anyone run into this before, or know what else could cause a target group to be unselectable despite meeting all standard compatibility requirements? Wondering if this is a known console bug.

Happy to share more details (ARNs, screenshots) if that helps troubleshoot.

re:Post Agent · Accepted Answer

The most likely cause of your target group being greyed out is that it's already associated with another load balancer. A target group can only be used with one load balancer at a time. Since you mentioned that all three target groups are currently attached to another working ALB in the same account and region, this is preventing you from selecting them for your new ALB.

To resolve this issue, you'll need to first disassociate the target groups from the existing ALB before you can attach them to your new consolidated ALB. Once a target group is no longer in use by the original load balancer, it will become selectable in the console for your new ALB.

For your consolidation approach, here's what you should do:

1. Create new target groups specifically for your new consolidated ALB (you can create them with the same configuration as your existing ones)
2. Update your ECS services to register with the new target groups
3. Configure your new ALB with the appropriate host-based routing rules pointing to these new target groups
4. Once everything is working and traffic has been migrated, you can decommission the old ALBs and their associated target groups

Alternatively, if you want to reuse the existing target groups, you'll need to:

1. Remove the target group associations from the old ALB's listeners
2. Wait for the target groups to become available
3. Then attach them to your new ALB
4. Finally, delete the old ALBs once they're no longer needed

This is a prerequisite for adding listeners - you cannot use the same target group with multiple load balancers simultaneously.  
**Sources**  
[Create an HTTP listener for your Application Load Balancer - Elastic Load Balancing](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/create-listener.html)

Takahiro Nozaki · Answer

**A likely lead: Issues caused by browser tab or session states have been reported.**

You mentioned trying multiple browsers (Brave, Firefox), but please check if you have other ALB-related tabs open within the same browser (such as a target group editing screen or the configuration page for a different ALB). The console's frontend might be carrying over edit locks or cached session information from those other tabs.

**Another strong hypothesis: The ALB itself has not yet reached the "Active" state.**

Newly created ALBs may remain in a "provisioning" state (not yet fully active) immediately after creation. If you attempt to select a target group on the listener/rule configuration screen while in this state, the console might display the target group but disable (gray out) the selection option until the ALB is fully ready.

How to verify: Go to the EC2 console > Load Balancers list and check if the "State" column for the ALB in question is fully **"Active"**. If it still shows "Provisioning," wait a few minutes and try configuring the listener again.

The most reliable troubleshooting method: Try the same operation using the AWS CLI.
To determine whether the issue is a console UI bug or an actual rejection by AWS (such as an overlooked compatibility issue), the most reliable approach is to attempt the same `create-listener` or `create-rule` operation via the CLI.

```
aws elbv2 create-listener \
--load-balancer-arn  \
--protocol HTTP \
--port 443 \
--default-actions Type=forward,TargetGroupArn=
```
* If the CLI operation succeeds, it proves that the issue is definitely a console UI or display glitch and that there is no problem with the actual configuration. After that, if you reload the console, it should appear with the changes correctly reflected.

* If the CLI also rejects the operation, it means there is an actual compatibility error you overlooked; in that case, the error message (specifying the exact reason) will provide much more useful information than the grayed-out state in the console.

Target group greyed out / not selectable when configuring listener rule on new ALB, despite matching VPC, subnet, and protocol

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