Hello,

The example code you're using never specifies which Request Item to attach this file to.

Try something like this:

var base64String = "...."

var attachment = new GlideSysAttachment();

var gr = new GlideRecord("sc_req_item");

gr.get('aeed229047801200e0ef563dbb9a71c2'); // Replace this with desired sys_id

// find the corresponding record

var attachment_sys_id = attachment.writeBase64(gr, "test.pdf", "application/pdf", base64String );

gs.log("system attachment id:" + attachment_sys_id);

Replace the sys_id with the sys_id of the record you want to add this attachment to.