If you have setup the trace using rollover files including a max number of files to use, you will have to read the first file before the rollover reaches the max number of files and starts over using the first again. Look at the datetime the files were last modified to see if this has happened.
There could be aanother issue with the filenames, see BOL:
Be aware that the fn_trace_gettable function will not load rollover files (when this option is specified by using the number_files argument) where the original trace file name ends with an underscore and a numeric value. (This does not apply to the underscore and number that are automatically appended when a file rolls over.)
Can you show us a list of the trace files in a post. Include the datetime the files were last modified.