Error communicating with device

Can anyone help with this problem? Not sure if it is a Calibre problem or a Calibre Companion problem or a Galaxy Note problem.

My Galaxy Note 10.1 (Android 5.1.1) has stopped accepting books from Calibre into Calibre Companion. It connects just fine, appears to sync just fine, but I can’t send any books (I've tried several in case it was just one book). I thought it might be the sd card, so I changed the cc library to main, but still no joy.
(NOTE: My Lg gpad x8.3 (Android 5.0.2) accepts the books into cc just fine.)

Here is what Calibre has to say.

calibre, version 2.60.0
ERROR: Error: Error communicating with device

[Errno 10053] An established connection was aborted by the software in your host machine

Traceback (most recent call last):
File "site-packages\calibre\gui2\device.py", line 87, in run
File "site-packages\calibre\gui2\device.py", line 584, in _upload_books
File "site-packages\calibre\devices\smart_device_app\driver.p y", line 50, in _synchronizer
File "site-packages\calibre\devices\smart_device_app\driver.p y", line 1452, in upload_books
File "site-packages\calibre\devices\smart_device_app\driver.p y", line 689, in _put_file
File "site-packages\calibre\devices\smart_device_app\driver.p y", line 575, in _send_byte_string
error: [Errno 10053] An established connection was aborted by the software in your host machine

Any help would be most appreciated.