The two most common issues when the drag and drop-feature doesn’t work are:
In Windows Soundly needs to run with the same permission level as the corresponding program you wish to drag and drop to. Try changing the permission level for Soundly on Window to Administrator. If Soundly is already running as Administrator, try changing it to User.
Soundly does not have permission/ability to save copies at the designated storage location Go to Window -> Settings -> Audio Storage Location in the Soundly software, and try changing the audio storage to a different folder.