MacDroid - Can't transfer files to my Samsung Galaxy A55

Hi guys, Does anyone know what I'm doing wrong to get this error message when dragging and dropping files into my music folder on my phone? This happened with my older android phone too, but worked fine on my S21 FE, I've enabled USB Debugging in developer options, my phone is only visible when I change it to USB tethering instead of transferring files/android auto. Get the same message when trying by Wi-Fi too, can't work out what I'm doing wrong :( https://preview.redd.it/386fto1aquce1.png?width=2499&format=png&auto=webp&s=5a4d1f3538d45d34748bb2084b70d434d59dcb5b Any help appreciated!