This link to an item on the Swift Ground Analysis table
does not exist for one of the following reasons:

1) NON-ASTROPHYSICAL TRIGGERS:
 The trigger is a due to non-astrophysical sources (eg noise,
Cosmic Ray Shower in the instrument, StarTracker Loss-of-Lock,
FSW Bug, Gyro Problem, etc), and as such, the BA_script output does not exist.
(Please note that this is not true for ALL non-astrophysical triggers;
some of them do have the automated processing results available.)

2) TELEMETRY GAP:
The data was never received on the ground.
This is a common explanation for the ~5% of the TDRSS Lightcurve links.

3) EARLY FLIGHT SOFTWARE:
In the first few months of the mission, the flight softwre did not produce
(or was enabled to produce) some of the data products to produce
these high-level data products in this table.

4) EARLY GROUND SOFTWARE:
To produce the files for this web table, two pipelines must 
be run on the data.  The entire 3 years of the mission was reprocessed
with the 2nd pipeline, but not with the 1st pipeline.  As such,
there are some intermediate data products produced by the later version
of the 1st pipeline that are needed for the 2nd pipeline.
Since nearly of this has to do with the TDRSS lightcurve data product,
it is uncertain if it worth the effort to re-process the entire 3 years
with the latest 1st_pipeline just to get these TDRSS lightcurves
which are obseleted by the much better event-by-event based mask-weighted
lightcurves.

5) EARLY (POST-LAUNCH) CONFIGURATION and OPERATIONS:
For the very early bursts (Dec 2004 and early Jan 2005), 
the TDRSS data products and some of the full-data_set products
do not exist because we had the thresholds turned up high 
during the post-launch checkout phase.  And as such, BAT did not
(could not) go through the normal on-board triggering and response
actions.

6) MISC:
And then there are a handful of links that do not exist because of
some "hiccup" in the automated processing which generated these 1000's
of data products and links.  We have tried to process the data
by hand when we have found these "hiccups".