TurboTax can not make a reFile change that is costing me $15,000

There was an error completing my tax return which was then netfiled. Now I need to make a change to my return and re-file but the software can't make the needed change. The product expert I spoke to on the phone could only screenshare and walk me through the process but there isn't a process to make the needed change. I tried starting a new return and it shows me the correct number, but I can't submit two tax returns. I need the re-file to amend my filed return in a way that it seems like it cannot do. Alternately if I'm given a code for a free return then I can complete my second (accurate) return, print it, compare all the fields, and use the CRA website to manually change what needs updated. I would be satisfied with this resolution as an alternative to trying to make the program do something it might not be able to do.