Error 404 not found means that the referenced GRIB file (aka Tidetech area) could not be found on the Tidetech server. That could stem from three possible situations:
1) The catalog is out of date, for example if Tidetech changed their catalog layout. WeatherTrack updates that catalog about daily, but this might fall in between updates. You can force a refresh by pulling down the list of Tidetech areas until the refresh icon appears.
2) You did tap refresh on an already downloaded GRIB file after Tidetech changed their catalog. You will have to download the area of interest again, this time with the changed Tidetech area.
3) Tidetech may happen to have a server problem and the file is simply not online. Either try again a little later or contact firstname.lastname@example.org
to check with them with the availability of the selected area.