Go to the Binary Header tab and look at the value in the Start Time field. Enter the correct value or simply try entering ‘0’. Click <Apply To Preview>. If the preview now displays something, proceed to define format (see Import Wizard Step 1b - Trace Header Tab and Import Wizard Step 1c - Binary Header Tab). Double check your start time setting after you finish defining the format on the Trace Header tab.
If you still have no preview, are you sure that this is a SEG-Y file? You may have inadvertently opened another file type.
What do you want to do?