The 2204a is a low memory device, so we will need to use streaming mode to capture the data to the PC. To do this just use the following settings :-
Across the top
100ms/div x100 1MS
At the bottom
and then make sure that
Tools->Preferences->Sampling->CollectionTime is set to 100ms/div
The trace will now draw across the screen, which is zoomed at the trigger point so you can see the actual data, and hopefully you will have decoded data. You can move the trigger position, and zoomed area, around to make sure you see the full data packet.
If you still have difficulty please post a data file so that we can check the settings, File->Save