SQL get_clob_from_file - Can I do this for a file on QNTC from a linux machine?

So thankful for the response to my last question. I'm banging my head on some of the nuances of get_clob_from_file.

We have successfully used the get_clob_from_file on the IBMi. Where I have manually placed the JSON on the IFS. We are attempting to automate the process.

We run PHP code on a linux machine. It reaches out to the cloud to pickup the json.
I have successfully picked up the file and placed in a windows server folder which is also mapped via QNTC.

I have successfully (with the help of a PTF) used get_clob_from_file with the file on the QNTC folder mapping via run scripts.
But I have not been able to get this to work from the PHP code. I do have an example that works from a native folder mapping on the IFS.

My unsuccessful statement looks something like this:
INSERT INTO RTL
(SQSID,CLQDATA)
VALUES ('SQSID',get_clob_from_file('/qntc/windows_server_folder/19b868fe.JSON')) WITH CS");

I get an SQL0443 - *N in *N type *FILE not found.

Is it not possible to do this? Or is there some nuance in the file path that I don't understand?

Thanks.
Vicki Wilson