From a search on the topic:
So far I had no joy so I dug around. There is a command line futility that can solve the problem if you grit your teeth and hold your tongue sideways.
1) Open a CMD prompt as adminstrator.
2) Visit the "C:\Program Files\Windows Defender" folder.
3) "dir *.exe" should show "mpcmdrun.exe". He is your best friend of the moment.
4) "mpcmdrun -?" gives a list of commands. Near the bottom are the interesting parameters. "-restore" says you want to restore.
mpcmdrun -restore -listall
This shows a list of quarantined items.
mpcmdrun -restore -all
This restores ALL quarantined items. Be afraid. Be very afraid. But it can be useful.
mpcmdrun -restore -name "fu.bar"
This will restore fu.bar to its rightful place in the universe.