The original Bluetooth LE sniffer firmware from Nordic had some restrictions such as only being usable by Wireshark 1.

As of August 2018 we are only selling Sniffers pre-prorgrammed with Firmware version 2

However, we'll keep this documentation up in case its useful for people with old boards

If by chance you have an nRF51822 board you want to load the firmware on, here's a hex that does not require the 32khz crystal (but does require the 16 mhz crystal)

Again, we don't have a guide or tutorial on loading the firmware onto an nRF51. We don't have the original source code, that hex is from Nordic and they only release hex files