With all due respect to other opinions, there probably is not much that is 'wrong.'not too sure whatwent wrong honestly.
And still not too sure what’s the next step unfortunately so do I call immigration ? Ircc? Long wait but if it’s the only way to get answers! Don’t have a choice
The fact that the ETA was issued is where the system messed up - it should have identified the child as a citizen but didn't - and with the ETA, the child boarded the plane. CBSA officers clearly didn't have an issue - even though they understood it.
You've submitted the citizenship application already - wait for it to get processed.
There is the possibility that you / your spouse should have indicated the child was a Canadian citizen when applying for the ETA - but they are not going to deny the child citizenship (as a minor especially) because of that. One of you could potentially be 'in trouble' for not declaring the child as a citizen when applying for the ETA. But I strongly doubt that IRCC is going to bother with pursuing that, and it would likely have minimal chance of being successful as a charge - because that statute likely requires intent and you'd just say 'we didn't realize.' And then the next step to this is that, basically, 'no harm was done' - it's hardly a problem that a Canadian citizen of minor age was ... admitted to Canada.
Now there are cases where inadvertently leaving something out would be misrepresentation and potentially serious consequences - but in this case, now that it's basically resolved, probably not.
So I'm going to suggest: wait it out and don't worry. Any 'mistakes that were made' or things that shouldn't have happened here have, likely, minimal or zero consequences for you, your husband or the child. It's not (IMO) even worth seeing a lawyer.
That said: my one suggestion would be that it's probably best if the child doesn't leave the country (necessitating return by AIR, and use of the ETA) until his citizenship is sorted. Just a risk of being stuck abroad. Returning by land to Canada should be okay (but also best to avoid, if possible).