Same problem... Also disabled SSL and ensured Drag and Drop was selected.
Ran as admin, elevated always. Win 10 Pro 64 (Server) , OSX 10.12.3. Version 1.8.8-stable-25a8cb2 Build Date: Mar/16/17
This is a blocker issue for me.
Drag-n-drop was the Primary reason I made the purchase in good faith.... since there is no trial option.
What are my refund Options?