Note that, by default, a BEEP base is registered to BEEP’s global TTN application. To add it to your own TTN application, I assume you set up your own AppEUI and AppKey in the device and added payload formatters and the HTTP integration as per BEEP’s instructions.
Aside: by default the base has ADR enabled. This does not work well for non-stationary devices, so may not work well when using it with TTN Mapper for testing. I don’t know if you can disable that.
Also, transmitting its total packet size of 59 bytes every 1 minute won’t adhere to TTN’s Fair Access Policy. On SF12BW125 thee 59 bytes only allow for one transmission every 2 hours. But even on the best data rate, SF7BW125, you’d be limited to one message every 6 minutes. For testing, this is not a problem though.