Doing a factory reset will force the device to dump its keys and get new ones.
or
Update to v3.5 or later firmware (currently v3.6: https://docs.sparkfun.com/SparkFun_RTK_ … re_update/). There was a bug in earlier versions that caused the key update routine to fail. But the initial key gathering works; that’s why #1 above works. If you erase the keys, the initial key gathering is triggered.