from_blob is right, but you have to make sure

that your array element datatype is indeed float
using from_blob requires you to keep the pointer array alive for the lifetime of the returned tensor. If that is a problem for you, you might try copying…
I’d probably print the converted tensor, too, just to be sure. I have stumbled over OpenCV giving me BGR in C++ while my model expected the RGB I got in Python and so.

Best regards
Thomas
P.S.: Nowadays we use torch.tensor in Python instead of the constructors.