new to airdroid. cannot transfer mp3.question

i just signed up to airdroid and installed it on my pc and my galaxy 4. when i launch it on my pc it shows my phone under "my devices".

the large section in the airdroid app says "drag & drop files here to transfer". however, when i try to drag and drop an mp3 (or any other type of file) there, my curser turns into the circle with a line through it.

can anyone explain why? what am i doing wrong?

thanks in advance from a noobie.
 

never mind. it looks like i can do it through the web based application. don't know why the pc based one does not work. 

anyway, it works through a browser.
 

Sorry that we are still looking into the cause of drag & drop files issue on AirDroid Win/Mac. If you want to transfer files with AirDroid Win/Mac, click the file icon, select the files to transfer. More detailed guide: http://help.airdroid.com/customer/portal/articles/1781974-file-transfer