How come Smartifi is still not compatible with AC56U? Is this model missing the ASSIA agent or the CloudCheck app simply needs an update to support this router?
The app is saying the only supported asus routers are AC3200, AC66R/U/W, AC68P/R/U/W and N66R/U/W.
It's possible that Asus didn't license out the client for that model. It's typical for manufacturers to have to pay for each different model they want to support. I wouldn't know for sure, I only briefly played with it, and found it to be rather useless, especially with Asus now having their own Android app for router management.