I have two new installations in different environments that I am experiencing a similar issue with.
Initial/testing installation: osTicket on Windows10 + IIS direct from osTicket website.
Production installation: osTicket Awesome theme on WinServer2019 + IIS from osTicket Awesome theme's website.
From the public-facing website/form, I can create a new ticket and upload+attach a file to it as an anonymous user with no issue. The file uploads to the form, the ticket + attachment is submitted and created with no issue.
Once that ticket is created, and while logged in as a Staff member, I am unable to add an attachment to the ticket for a reply. I am given a "File Upload Error undefined 413" error message. I have checked/modified the php.ini file to enable file uploads, and set the max file size higher. I have gone into the osTicket attachment settings and verified that nothing is in the "optional" fields for allowing or blocking file types, I have also changed the max file size to reflect the modified php.ini settings. I previously had the system configured to save attachments to the database and have also tried changing it to save them to the local file system in a new folder I created with full read/write permissions as well, but nothing solved the issue.
I discovered this issue while trying to create an FAQ entry where I wanted to include some attachments and received the same error. I then tried attaching the file to a ticket and found it to have the same issue. The error is received while the site is uploading file to the site, prior to hitting the Submit button to create/modify the ticket or FAQ entry and occurs regardless of file type chosen (tested with pdf, jpg, exe). I have noticed that I seem to be getting a ticket lock expiring soon notice right after the error as well, regardless of how close I am to that timer expiration, but I don't know if it is related to this issue.
Exact error given:
File Upload Error
Any advice would be appreciated!