Do you receive any error messages? If so, please tell us the exact text of the message. If not, please describe what you mean by "the search fails".
If it appears that the caches are downloading but not loading into GSAK, click the "Advanced" tab of the Get Geocaches dialog and check your Load settings (click the "settings dialog" button). From the information you gave, it seems that the caches may be downloading but not being loaded (e.g. perhaps your load settings are pointing to the wrong folder?). Try selected "* User GSAK defaults *" for the Load settings drop down on the Get Geocaches dialog Advanced tab and see if that cures the problem.
If it appears that the caches are downloading but not loading into GSAK, click the "Advanced" tab of the Get Geocaches dialog and check your Load settings (click the "settings dialog" button). From the information you gave, it seems that the caches may be downloading but not being loaded (e.g. perhaps your load settings are pointing to the wrong folder?). Try selected "* User GSAK defaults *" for the Load settings drop down on the Get Geocaches dialog Advanced tab and see if that cures the problem.