RNE-L21 imei repair 8.0 prob

Checking IMEI(s)...
Authenticating...
This may take a while.
Be patient! Do NOT disconnect the phone!
The device sent an invalid challenge.
Retry 2/5
The device sent an invalid challenge.
Retry 3/5
The device sent an invalid challenge.
Retry 4/5
The device sent an invalid challenge.
Retry 5/5
The device sent an invalid challenge.
Authentication with the device failed.
Finished at local time: [09.03.18 11:44:32]
WorkID: 43453121

Model RNE-L21 V 8.0
chimera team pless help me abut this erro