Kobo Arc 7 is no longer detected, used to work

[Porcelain Mouse]

When I bought my Arc 7, it worked on all platforms. Over time, however, support has deteriorated. It first developed a problem with MTP mode, so I used "camera" mode. But now, Calibre just doesn't recognize my device at all. I checked "ignored devices" and it is empty.

In the past, I have tried hard/full reset of the device many many times and that doesn't seem to help.

Here is the output from the "debug device" option in Miscellaneous:

calibre 2.31 isfrozen: True is64bit: True
Linux-3.18.3-201.fc21.x86_64-x86_64-with-fedora-21-Twenty_One Linux ('64bit', 'ELF')
('Linux', '3.18.3-201.fc21.x86_64', '#1 SMP Mon Jan 19 15:59:31 UTC 2015')
Python 2.7.9
Linux: ('Fedora', '21', 'Twenty One')
Successfully initialized third party plugins: Overdrive Link && Overdrive Link
USB devices on system:
[['0x510', '0x32', '0x110', u'SEJIN', u'SEJIN USB joint Keyboard', u''],
 ['0x1b1c', '0x1b05', '0x226', u'Corsair', u'Corsair M65 Gaming Mouse', u''],
 ['0x5e3', '0x732', '0x551', u'Genesys', u'USB Reader', u'000000001398'],
 ['0x2237', '0xc108', '0x255', u'Kobo', u'arc 7', u'SSTGTKWSS4SO4HT8'],
 ['0x46d', '0x81b', '0x12', u'', u'', u'AAB2FDA0'],
 ['0x1050', '0x10', '0x224', u'Yubico', u'Yubico Yubikey II', u'0000976793'],
 ['0x451',
  '0x3410',
  '0x101',
  u'Texas Instruments',
  u'TUSB3410 Boot Device',
  u'TUSB3410'],
 ['0x764', '0x501', '0x1', u'CPS', u'CP 1500D', u'']]

No disabled plugins
Looking for devices of type: MTP_DEVICE
Unknown device USBDevice(busnum=3, devnum=2, vendor_id=0x2237, product_id=0xc108, bcd=0x0255, manufacturer=Kobo, product=arc 7, serial=SSTGTKWSS4SO4HT8) claims to be an MTP device
MTP devices connected:
USBDevice(busnum=3, devnum=2, vendor_id=0x2237, product_id=0xc108, bcd=0x0255, manufacturer=Kobo, product=arc 7, serial=SSTGTKWSS4SO4HT8)

Trying to open: USBDevice(busnum=3, devnum=2, vendor_id=0x2237, product_id=0xc108, bcd=0x0255, manufacturer=Kobo, product=arc 7, serial=SSTGTKWSS4SO4HT8)
Opened arc 7 successfully
Storage info:
[{'capacity': 6133600256L,
  'freespace_bytes': 4170870784L,
  'freespace_objects': 1073741824L,
  'id': 65537,
  'name': 'Internal storage',
  'removable': False,
  'rw': True,
  'volume_id': None},
 {'capacity': 31423037440L,
  'freespace_bytes': 28514222080L,
  'freespace_objects': 1073741824L,
  'id': 131073,
  'name': 'SD card',
  'removable': True,
  'rw': True,
  'volume_id': None}]

[Kovid Goyal (kovid)]

According to that the device is being detected successfully. Run calibre
itself in debug mode (right click the preferences button) and then pot
the log when you try to conenct the device.

 status incomplete

[Porcelain Mouse (pmouse)]

Hi Kovid,

Sorry for the trouble. I found that connecting the Kobo to another USB port, got me back to the previous situation where Calibre reports and error communicating with the device, but does try to communicate.

I don't understand how some USB ports are different from others. Any insights you have about such things would be appreciated.

Regardless, this symptom is gone and I don't think it's a Calibre bug.