If you are using a Google Chrome web browser there is a probability that the browser will not be able to download the software for the manual update.
If you are using a Windows based personal computer switch your browser to Edge and it should download.
TurboTax support FAQ for a 2020 manual update (Windows) - https://ttlc.intuit.com/community/updating/help/manually-update-turbotax-for-windows-software-basic-...
