I'm also having the same issue with the slave unit going red. I've moved it closer and it doesn't make a difference. Hopefully the beta that is on the Global forum is usable in the US? I might try...

@Tony Hi Tony, I have the same router and looked at the settngs you suggested and do not see the 10000 Full Duplex on the drop down menu. Below is what I see. Thanks Frank

@taylord_79 Looks like you missed the first part of the email address, to me the address should be Support.USA@Tp-link.com. You didn't include the support. part of it.