This happens when Conn can no longer locate the relevant file in the file location it was when you selected it for import to Conn. So likely the "referenceT1.nii" file got moved after you selected it in Conn. 

If the file is no longer in this directory (/Users/faeze/Downloads/app/conn/utils/surf/referenceT1.nii), you will always get this error. You should be able to press "Continue" on the error message and reselect the file location where the T1 actually is.