I had the same thing on my device. However, I noticed that there was a flashing icon in my notification area at the top. When I swiped down, the message asked if I wanted to Seize control of the ANT radio. When I tapped on this, I got another prompt that said that another application has control of the ANT radio and did I want to seize control. When I tapped yes, the message changed from Requires ARS to AUM1.04B22.
So, if another app is running which as seized control of the ANT radio, you will see the Requires ARS message in ANT Tester. This was running version 1.4 of Ant Tester installed from the Play Store.