From the message, it seems that the text file resides on a remote SAS server. Is that correct? The message indicates that EG cannot read the contents of the file, because in order to read the file it would have to transfer it from the remote server to your local server. That operation would be expensive because the file is so large, so EG "skips" that step.
If you have access to the file from your PC, say on a network share or mapped drive, then EG should be able to preview the contents of the file. Simply select "Local Computer" instead of "SAS Servers" when selecting the data file.
Chris