@José-Luis31
I hope you are well! You probably won't get very far with Airbnb support, as you have already found out- so well done for coming here.
There may well be a glitch in the co-hosting system- as there very often is!
Have you asked the primary host to re-send the invite for the second listing?
I suggest that she does this until you're able to finally accept the invite and see the listing on your profile....it might take more than a few tries.
This usually works for me when there is a glitch in the system.
Paul 🙂