Android App - can not open any unattended computers from list

Android App - can not open any unattended computers from list

Hi
One of our employees has 3 x computers in his unattended list, available and working from the computer / web based system without problem.
However in the Android App he can not click to open any of these computers, it simply does nothing, tap on the computer name (online with green icon) and literally nothing happens.
He has a Nexus 5X phone on Android 6.0.1
However I myself have a HTC 10 also on Android 6.0.1 and it works fine.

Any ideas what we can try on his phone?