This problem (zero values or constantly flat values) sometimes occurs with the FYTA Beam G1 when the ground rods do not have good contact with the sensor. Unfortunately, this can happen and is due to the fact that the rods are interchangeable. It is similar to a computer monitor when the cable is not properly connected.
Here's how you can fix the problem:
Open the battery compartment and remove the button cell from the sensor.
Press lightly with your finger on the lower battery contact so that the small circuit board moves down slightly.
Reinsert the button cell battery, close the battery compartment, and ensure that the LED lights up.
Unscrew the soil probes and then screw them back in tightly. Make sure that the washers are positioned well. You can also use small pliers to help you fasten the soil probes.
Then gently tap the sensor with the rods on a table a few times.
Take a metal object and touch both soil probes at the same time to shorten them. Meanwhile, start Live Mode and check the readings. The soil moisture should now show a value above 70% (If you have set a mineral substrate, it should even be up to 100%).
If you saw a solid value in step 6, put the sensor back in the soil. If not, repeat steps 1-6 and adjust the ground rods slightly.
Now restart Live Mode to check the measurement once again.