So my app was working (was able to upload file to a Google Drive folder). But today, it doesn't work all of a sudden. Whenever I want to upload the file, it keeps saying "server rejected" which I'm not sure why.
I use drive picker and onPickerInit, this is what I put as a custom action:
var folderId = "1t6MrDgiWj0tHEEX0QgxhLerDuDIht1gPPP"; //the desired folder id - I put a fake Id
pickerBuilder.SW.Vq["0"].mc.parent = folderId;
I just put this on the server script and it fixes the problem:
function writeAccess() {
DriveApp.addFile();
}