Radio Frequency communication may come and go occasionally. This can be normal in some environments (e.g. moister climates). If transmitter signal is lost, please wait 2-4 hours for the signal to reconnect on its own.
Here is a link to the User Manual for your product.
https://www.lacrossetechnology.com/media/catalog/product/w/s/ws-8119u-it__faqs_1.pdf
try new test leads first. even if the unit is miscalibrated, you should get the same measurements from the same components/circuits. you'll need to send the unit to a calibration center, or the manufacturer, to get it zeroed out, if you still need to afrer getting new test leads
1. Disconnect the test leads from any energized circuit and then from the instrument.
2. Turn the range switch to the "OFF" position
3. Slide off the back case battery cover.
4. Remove the battery from the compartment and unsnap the battery connector.
5. Replace the battery with a 9V transistor type battery (NEDA # 1604), For maximum battery life, alkaline cells are recommended.
6. Reverse the above procedure to complete replacement.
Not sure but if you press the clock button on the side;
? Press to start or stop a WWVB time signal search (which is what I think your clock is set to)
? Hold for 3 seconds to set time/calendar, etc.