I was able to use sen2cor v280 by moving my data to C: (dunno why that is a requirement) but it gives me this message:
Product metadata file cannot be read.
The filename is S2A_MSIL1C_20170614T112111_N0205_R037_T29TPF_20170614T112422. I compared it to newer L2A and it is the same convention. So, why is it not finding the product metadata? An output is created, though, but it is the same as the original file.