Yep---that was it in my case. I had the same error but it went away after upgrading to MacOS 12.5. You should actually check if your PyTorch installation can detect the mps backend: `torch.backends.mps.is_available()` must be equal to True.
That might have to do with your Mac OS version. Pre-12.4 Mac OS does not allow the Torch backend to use the M1 GPU, and so the script attempts to use the cpu, but then the cpu does not support half-precision numbers.