No data is collected due to error messagfe while counting. Or no or empty data appears in the data file.
Follow the instructions on page Hardware does not work in order to figure out hardware problems with the counter box or histogram memory.
If this is OK and a histogram memory is involved follow the instructions on page Interacting with the histogram memory WWW interface. Only if there are events collected in the histogram memory and data does not arrive in data files a software problem is to be considered.