First off, check for any offsets that may still be entered in the gauge.

Make sure you took a standard count and it passed.

If working on soils you may have a situation where the gauge is viewing natural hydrogen as moisture. Soil with high amounts of mica is an example.

Working on frozen materials can fail due to the expansion of moisture. This will lead to higher moisture content and lower density readings.

Asphalt mats with significant surface voids can also be a problem. Use sand or fines to fill in these voids and dampen the effects of the voids.

Make sure to source rod is well seated in the appropriate depth rod notch.