First off, are you sure that you did turn on the trace in the first place? When you run ‘st01’ it displays the trace status in a text field, this should say “Trace switched on…”.
If it is turned on, did you have one or more of the trace components ticked when you turned it on? These are listed on the initial screen, e.g. Authorisation check and Table Buffer Trace. If none of these are ticked you’re not going to be tracing anything, hence no results. You also need to check the filters that you have set (on the same screen there’s a “General Filters” button which allows you to set these) when turning the trace on. If you’re restricting by e.g. a username, perhaps there’s been no activity for that user.
Finally you should also double-check what filters you have applied when looking at the log. Click on the “Analysis” button to look at the log, this will bring you to a selection screen. Make sure you have no filters applied here before clicking Execute; e.g. your own username is usually filled in by default, this means that it will only return log entries generated by your userid. Again, also ensure that you have one or more of the Trace Records ticked (the same list as the Trace Components on the previous screen).
SAP Basis Consultant