Description
Check that you have correctly identified the dataset and that you do have read permission. If the path and permissions are okay, the next possible source of the problem may be the result of missing any required component files for that format. It is also possible that the raster has been internally corrupted.
Solution
Check that you have correctly identified the raster and that you do have read permission. If this has been done and the problem continues, you should then determine whether the raster is valid. First try displaying it. If you cannot display it, check to see that all the required component files are present. If it seems that the raster data has been corrupted, you may need to re-create it. Hopefully, you have a backup copy that can be used, or you can run the process that created it again.