Apologies for the delay coming back to you on this one.
Do you mean destinationDomains on the AMP tracker and page must include “cdn.ampproject.org”?
The honest answer is I’m not sure exactly where I was going with this - I was trying to narrow down the possibilities and figured that some configuration of the linker might be at root. But having reflected on that, this is not a good line to pursue, the value is in the querystring already. Apologies for the wild goose chase on that one.
I have since reaquainted myself with the project (like I mentioned it’s been a while so I’m rusty on AMP), and I have a hunch what might be going wrong here - the logic in there currently is to first write the value to a cookie, then try to read the cookie and send. If for some reason writing to the cookie isn’t allowed on the amp domain (eg secure cookie settings, or pre-existing cookie conflicts), then I think we miss the value when we try to send it.
I think we have a further problem with this since the order of operations isn’t necessarily deterministic.
There are two things that might help me confirm/deny this thinking:
Could you send across the exact value of the _sp parameter in the url?
Could you tell me if an _sp_duid cookie is being set in the browser, and if so what’s the value?
Ps. it would also be helpful to take a look at the actual page in question - since you’ve redacted domains in your message I understand you might not want to share.
If you’re able to send a link in a private message, that’d be helpful. If not, absolutely no worries