Hello, thash.
I appreciate you contacting the Community for support. I'd like to help make sure you and your colleague are able to see the same things in QuickBooks Online.
As an initial troubleshooting step, I recommend clearing the cache in your internet browser. The cache can sometimes get bogged down with data that is no longer needed, potentially causing viewing and performance errors within the system. This article provides the steps you need for this process depending on which browser you're using: https://quickbooks.intuit.com/community/Getting-Started/How-do-I-clear-my-browser-cache-and-temporar....
Let me know if you're able to see the copy option on the invoice after trying this. I'll keep any eye out for your reply.