If you are running SAS OnDemand for Academics, you have to pay attention when specifying the location path of the external file, as shown below.
The file path and file name are both case-sensitive.
SAS OnDemand for Academics runs on a Unix system.
The best way to ensure your path is specified correctly in your code is to look up the file location in the file properties.
You can find the exact file location in File Properties:
You can copy and paste the location path in your code.