This could be for a number of reasons. The solution depends upon the exact cause of the problem:

1. Ensure that the target has an ETM!
   
   
2. Ensure that your version of TDT is compatible with the ETM version being used. (please refer to the table from the FAQ: "What ETMs are supported by which versions of TDT?").
   
   
3. If you are using MultiTrace, make sure you are using the latest MultiTrace patch.
   
   
4. Check that TDT has been successfully installed by connecting AXD to an ARMulator target that is ETM enabled and check to see if ARMulator Trace is visible. If trace capture from ARMulator is visible then refer to the other possible causes listed below. If ARMulator trace is not visible then ensure that TDT has been correctly installed by uninstalling and re-installing the necessary components.
   
   
5. Check Trace capture has been correctly enabled. If inappropriate rules have been defined then the collection of trace data from the TPA may not be enabled. Try to re-define the trace capture rules to capture trace constantly the 'Enable Tracing' rule should always be defined.
   
   
6. Check connections with the TPA are correct. Check all the physical connections to the trace port analyser. Next ensure that the software is correctly configured to enable a successful connection to the TPA. For example, if using Multi-ICE with MultiTrace, check the 'Trace' tab of the Multi-ICE configuration dialog to ensure that the TPA is visible to the debugger.