For the time:
1. Make sure that your minimum lap time is not set too high.
2. Make sure that your knee or something else isn't blocking the sensor.
3. Make sure the plug is secure and the indent is up.
For the RPM:
1. Make sure the wire isn't rattling around against anything or in conduit.
2. If running animal make sure it isn't too close to the boot. Sometimes the coil is too strong and they work better moved back a bit.
3. Make sure the RPM wire is not run alongside the heat wire or other wires. They cause interference.
If all this fails send it to AIM and they will update the firmware and diagnose it for you. You only pay for parts and they are top notch!