What browser you are using? Are you using IE11?
Can you replicate this issue with other browser like firefox or chrome?
A) Please run the following File attachment test from the People tools page in order to see if there is something wrong with the setup of the file attachments mechanism.
Navigate to People Tools>Utilities>Debug>People Tools Test Utilities page and enter the following in the FTP URL dialog box:
Test it out by clicking on the Attach button to upload a file.
2) Please review following documents
A) Doc ID 1061860.1 - E-FTP: File Attachments Suddenly Stopped Working - General Troubleshooting Guide
B) 1282445.1 - E-FTP: ViewAttachment fails when accessed through Portal with Direct link to content.https://mosemp.us.oracle.com/epmos/faces/ui/km/DocumentDisplay.jspx?id=1282445.1
Note: This issue(View Attachment does not work on first click(throws 404 Error) but does work on second or third attempt) is experienced sporadically by the users in Production.
Browser version : IE 8
Agents/users are permitted to use only IE 8.0 in Production.
We are using a load balancer to switch betweeen 2 servers.
You haven't indicated what you have ruled out or even looked at from the previous responses. That said, if you know it is none of them, I would look to see if jolt pooling is on. It's always seemed to be a problem with attachments/file downloads in environments with multiple app server domains on different servers.