I'm assuming you are using the Desktop program since Online is not open yet.
You need to have the tax file ending in .tax2019 on your computer to transfer into 2020. Do you have the .tax2019 file? Are you on Windows or Mac?
Try starting a new return, File-New and see if you can transfer. If it doesn't find last year's file you can browse to where it is.
Here's an idea. Do you still have 2019 installed? Try opening 2019 program and see if you can get your 2019 return to show up in it. Go to FILE - OPEN. Then save it again with a name and place you can find. Go to File - Save As.
