Universal Links not opening the app

Hi. We have 2 apps in the store with universal links working fine, and we are readying the launch of a new version, essentially the same codebase but with different branding and into a different territory. however with this one universal links are not currently working. When the app is installed, swcutil shows the following:

App ID:               [REDACTED]
App Version:          331.0
App PI:               <LSPersistentIdentifier 0x5ccc0ee20> { v = 0, t = 0x8, u = 0x6b8, db = E038B2E7-CA87-4BA2-A129-C25394D0F72F, {length = 8, bytes = 0xb806000000000000} }
Domain:               [REDACTED]
User Approval:        unspecified
Site/Fmwk Approval:   denied
Flags:                
Last Checked:         2024-02-16 12:06:39 +0000
Next Check:           2024-02-21 11:08:37 +0000

suggesting the CDN was denied access, but if I query the CDN using

https://app-site-association.cdn-apple.com/a/v1/DOMAIN

I get the correct app-association contents back.

with the previous apps, they were well established before we introduced universal links, but this one is not yet available on the store. the debug build pointing at production seems to work (not using mode=developer) but the TestFlight build does not.

we are confident in the contents of the app-association file as it mirrors the other apps.

It's been suggested that this could be because the app is not yet available in the store. Is this the case?