Because delays add additional material to the end of selected audio (a delay tap), make a selection that is longer than the original source material so AudioSuite can write the additional delayed audio to the audio file.
Selecting only the original material, without leaving additional space at the end results in the delayed audio being cutoff at the end of the selection. To accommodate delayed audio that comes after the source audio, place the clip in a track, and select the desired audio plus an amount of blank space at the end of the clip equal to the amount of delay that you have added in the plug-in. The plug-in will then have space at the end of the clip in which to write the final delay.