For anyone else struggling with this on Windows, I found that completely disabling all other MIDI devices/ports/etc was needed before MIOS studio would communicate with LoopA. Firmware upgrade appeared to complete as expected (on restart, v2.09 is now displayed).
The numbers puzzled me though:
Trying to contact the core...
project.hex contains 270656 bytes (1058 blocks).
Range 0x08000000-0x08003fff (16384 bytes) - BL excluded
Range 0x08004000-0x080041ff (512 bytes) - STM32 Flash
Range 0x08010000-0x0804dfff (235952 bytes) - STM32 Flash
Upload of 254464 bytes completed after 5.03s (49.36 kb/s)
1 ignorable errors during upload solved (no issue!)
Where does 254464 come from?
Never mind, as long as it works 🙂