Error training pytorch lightning

Hi,
I got error when doing training using pytorch lightning.

>   File "C:\Users\XXX\anaconda3\envs\py310\lib\site-packages\torch\autograd\__init__.py", line 197, in backward
    Variable._execution_engine.run_backward(  # Calls into the C++ engine to run the backward pass
RuntimeError: element 0 of tensors does not require grad and does not have a grad_fn

Please advise,

thanks