For anyone experiencing issues with either the Smart Home or Smart Air Conditioning apps, I'd advise trying to connect your devices using the SmartThings app instead.
Our UK SmartThings site has helpful guides on how to set up appliances in SmartThings, as well as some troubleshooting tips, and contact details/links for the SmartThings team and the SmartThings Community here.
Just a couple of useful general FYI's to add, if you should encounter any SmartThings-related issues with your appliances:
Say "Hello!" to the Community in The Introduce Yourself Thread.