About "This file could not be uploaded" error on panel

Hello, I have a project where my coworker has setup an aws ec2 instance, and I have installed kirby on it. (the kirby is running on a apache server)

It did not have any problems while I was using an ip address to access the panel, but when my coworker linked it to a domain and installed SSL, there were some mixed-content errors and the panel would not show.

This problem went away when I was told by the coworker to use the wildcard option in config url parameter, but now uploading files does not seem to work anymore when I access the panel with the domain and https protocol. They fail with the error message “This file could not be uploaded”. When I check the browser console, a 403 error is printed upon trying to upload the file.

But the upload still works if I access the panel through the ip address with http protocol!

My coworker has setup the server settings and although I would want to ask them whether if some server configuration might have caused this, my coworker does not seem to know much about kirby.

Is there some common cause to this type of problem? I am thinking this could be a problem on the apache server configuration, but I don’t know what I should ask my coworker to do.
Should I tell them to check the error logs stored at the error_log directory?

The aws ec2 instance was connected to a cdn and my coworker informed me that some settings on the cdn side was causing this.

Also, we found that uploading new files worked in both cases and only the replacing file functionality was affected.