Latest DL manager? Check version:
https://www.pgmusic.com/support.updates.win.dm.htm

If yes ^
Try to run as admin.
Make sure download path is pointing to the proper drive. Simple stuff gets overlooked.
Uncheck "Automatically install downloaded files". Wait will all downloaded, press big yellow button on upper right "Install All"

Alternatively (I believe) you can go to C: (or whatever drive you have downloaded files) Usually in root, folder: BBDownloads
And if the files are there, just install packages manually. If this is an upgrade, should not be a long process.