You can check if the load cell is working or not by verifying two aspects of the load cell – load cell resistance and the load cell voltage.
Load cell output resistance is measured between the positive and negative wires. The load cell input resistance is measured between the positive excitation wire and the negative excitation wire. In both cases, the value between the wires must be equal or similar to the datasheet provided with the load cell.
To measure the load cell voltage, connect the two wires to the amplifier. Now measure the response signal between the positive and negative signal wires while incrementing the load to see the corresponding signal increment.