Downloaded SW2020 SP4 via Installation Manger failed, resorted to manual downloading of files, saved in location SW installation manager asked for, but now downloaded manually 6 times today, still IM is trying to re-download the files and failing, will not proceed using already downloaded files.

Error shown that I get on Installation Manger after it will not use the already downloaded files.

Installation files could not be downloaded because: General download error. If the problem persists, a proxy server might be preventing automatic downloads. Choose the option to download files manually instead.