Most GP8 Amp BVP (finger heart rate) errors are caused by improper placement of the finger in the sensor. Move your finger out of the sensor a bit, then a bit more. Switch which BVP sensor you are using or move the sensor to a smaller finger. You can also purchase an iFeel Sensor which works with the GP8 Amp as a highly accurate and very comfortable and easy to use heart rate source.
Most GP8 Amp ECG errors are caused by movements or poor conductance (move hair out of the way or change electrode location, clean the skin and sensor with alcohol wipes, move the electrode slightly). Please read the GP8 Amp User Guide for more information.
Also, make sure you have your heart rate source set correctly on the Alive Main Menu.
For a detailed tutorial on fixing common GP8 Amp heart rate errors please watch this video: