Is the date checked the date when the log was created on the web server or the date it was written to the WebLog Expert cache?
The program tries to re-download only new or changed log files, maybe there are some changes in your log files. E.g. if you use log rotation it may cause problems both with log download and analysis.
If your web server is located on the same network where the log analysis server is located, it is better to access log files via file share, in this case the program will read the logs directly from the shared folder.
The program uses log cache to store previously downloaded log files. Every time it needs to download a file, it first checks whether this version of the file is already in cache. The program checks not only the name of the file but also its size and date to determine whether the file has been modified since the last download.
If your web server is located on the same network where the log analysis server is located, it is better to access log files via file share, in this case the program will read the logs directly from the shared folder.