I don't know about Barclay's specifically, but both of my banking apps and my credit card app require "Exploit protection compatibility mode" to be toggled on to work with GOS. If you're up for trying it again, with the app installed, long press on it, select App Info, then scroll down and you'll see the option under "Exploit Protection".
I say this because it's not the GOS team who needs to fix the app not working, it's the app developers (and most of them aren't going to fix it.)