The specified feature class could not be successfully accessed. This may be due to incorrectly specifying the paths or not having permission to access the data folders. If the path and permissions are okay, the next possible source of the problem may be that the dataset has been corrupted.
Check that you have correctly identified the dataset(s) and that you do have read permission. If this has been done and the problem continues, you should then determine whether the dataset is a valid one. First try displaying it. If you cannot display it, try copying it or exporting it to a different format. If you cannot do either, it is possible the data has been corrupted and will need to be re-created. Hopefully, you have a backup copy that can be used or can run the process that created it again.