Sounds like you have a file path that is not valid for every computer on your network, but file access permissions could also be the cause of the trouble.
Is this a shared folder that is accessible to all your DB users that will be using this feature of your database?
Is that shared folder mounted/mapped in such a fashion that the file path to this folder is exactly the same on every computer?
If it's not a shared folder, but rather a local folder on each computer, you'll need to create identical folders with identical file paths or a file path to a generalized location such as the desktop or documents folders. And FileMaker cannot, by itself, create directories, only files. To create a directory requires setting up a database script to perform either a command line or system script to create the new folder.
Here's a thread on $path variables and container fields where you can download an exploration file that explores these concepts if you are interested: Exploring the use of a $Path Variable in Scripts