Are you using the Desktop program? Maybe last year you indicated it was sold or the Final year?
Here's an idea. Do you still have 2018 installed? Try opening the 2018 program and see if you can get your 2018 return to show up in it and if it is the right return. Go to FILE - OPEN. And see if your property is in it and if it's marked as finally disposed. Or any Assets were disposed or sold.
Then save it again with a name and place you can find. Go to File - Save As. Then start a new 2019 return FILE-NEW and transfer from the saved 2018 file.
