it looks like you are using the file mask within a file exists activity
file exists activity is not supporting a file mask
instead of use the following condition on the if activty only:
System.IO.Directory.GetFiles("\epic-nas.et1157.epichosted.com\xfr\nonprd\toODB\Claims\PBClaims\CRD\TEST1\archive", "EPICTRAN"+Now.ToString("yyyyMMdd")+"*.txt").Any()
and also recheck the parent folder path as we do feel that after archive the \ was missing in your sample, but we assume that the file name starts with EPICTRAN