Make sure you plug it into the same USB port every time - the one it was plugged into when you installed the software. Sounds daft, but I've seen the same problem before and the aforementioned was the answer.
Surface Pro (2017) vs Surface Pro 4
20 groundbreaking 3D animation techniques
How to mine Bitcoin on Mac
Synology invites you to visit them at Insomnia on 26th – 29th August. Book your tickets now and visit Synology.