You need the 2023 tax file ending in .tax2023 to transfer into 2024. There is no “export”. You start a new 2024 return and the first thing it should do is look for all files ending in .tax2023 on your computer to transfer. Are you on Windows or Mac?
How to transfer into Windows Desktop
How to transfer into Mac Desktop
There is a button which allows you to browse your hard drive so as to find the 2023 tax return and click on it. The most likely reason for this issue is that TT is looking for your 2023 tax return in a different place from where you saved it last year. People have all manner of filing systems for where they put their various files and, of course, TT does not know what system you are using. It looks in only one place and if the file is not there, it can't find it. You have to tell TT where to look.