After some trouble I got Windows 10 desktop to recognize my Blu Advance 5.0 but it shows most of the folders in Phone Storage and the SC card as empty, while at the same time indicating that both are almost full.
Ok, try this: Plug your phone to your PC using a USB cable on a different port. On your phone, choose Media Device (MTP) or USB storage. Let me know if that works.
More details: After installing driver for the Blu Advance 5.0 (hopefully the right one) I got this message in Device Manager: "Device USB\VID_0E8D&PID_2008\0123456789ABCDEF requires further installation."
No clue how to do "further installation" but something is clearly wrong since my desktop Windows Explorer shows most of the folders in Phone Storage and SD card as empty, while at the same time the phone is telling me they are nearly full.