Maybe I am misunderstanding the situation - if so please forgive me...
1/ the ARC PRO should automatically connect over Bluetooth as soon as the app is opened. This, of course, assumes the bluetooth function on the smart phone Has been enabled.
2/ if you use the usual bluetooth search and connect function inside the smartphone operating system then the ARC PRO will not show up. You cannot connect manually to it As you would when pairing other devices such as headphones etc.
3/ there is a useful app called BlueLight which you can use to scan for all bluetooth devices in the vicinity of the smartdevice including those which are normally hidden. Load this app and start scanning and then thevARC PRO should show up. Does this happen?