Hello, Txus Carrion-

I am not sure if you were able to find solution regarding this question or not.
This is most likely the RFD-8500 Bluetooth discovery has timed out and not longer able to pair. This will time out after about 30 seconds.

(1) Turn the RFD8500 on and ensure Bluetooth is enabled. If not,
(2) press the Bluetooth button on the RFD8500 for one second to make it discoverable. When discoverable, the Bluetooth LED slowly flashes blue.
(3) On the Android or Apple IOS device, look for the RFD8500 in the list of available of discovered devices.
(4) Touch the RFD8500 that is associated by Serial Number to the unit you would like to pair to.
(5) During the pairing of the (2) devices, the RFD8500 Bluetooth LED will start flashing very fast. You will now need to press the trigger of the RFD8500 to allow the pairing to take effect.- You should now hear a (Beep) acknowledging that this was successful event. There now should be a steady Blue LED light on the bluetooth button.
(6) Exit the Bluetooth settings page of the mobile Device Settings screen and now run the RFID Demo Application.
(7) From the Demo Application, select Settings > Readers List and confirm the RFD8500 serial number with which you paired is now showing up and displayed.
(8) You now can check the box and allow the RFID reader to connect and read tags,

Below is link for the RFD8500 support page regarding downloads and firmware updates to the device.
-Thanks,
https://www.zebra.com/us/en/support-downloads/rfid/rfid-handhelds/rfd-8…

Hi,

I suggest to factory reset the RFD8500 and start over according to the user guide.