This error likely happens when you switch your Google Apps Script project to use Chrome V8 engine which is currently not compatible with Forms library.
To resolve the issue, open your Google Sheet associated with File Upload Forms. Go to Tools > Script Editor.
Inside the Script Editor, go to the Run menu and choose "Disable new Apps Script runtime powered by Chrome v8"
Next, go to the Publish menu, choose Deploy as Web App, select a new project version and click the Update button.
The error should no longer appear.
Nathaniel T Johnson
I setup my File Upload Form form and when I try and view the link it gives me this error in Google Apps Script