I suggest you review previous Github issues
  https://github.com/rordenlab/dcm2niix/issues
for example
  https://github.com/rordenlab/dcm2niix/issues/429
if these do not resolve your issue, create a new Github issue - the new issue template guides you through details that will improve troubleshooting. With Siemens enahnced DICOMs it is critical to know your software (XA10 was buggy and underspecified, while XA30 is much more complete) as well as the mode that data was exported as described here
  https://github.com/rordenlab/dcm2niix/issues/236
These reflect limitations in the files created by Siemens, though recent releases of dcm2niix includes kludges to mitigate these.