Thank you for your response.

I have tried QBO in Firefox and Chrome as well as Incognito mode in both with no luck.

I also tried chat tech support and after an hour and a half the answer I got was: "I really apologize for taking so long. Upon consultation regarding the issue, there might be an update that Quickbooks has made. Currently no option to bring back the flat rate. A product limitation. However you may send a feedback regarding this. I’m truly sorry to hear about your experience."