Error Syncing to iPad after Updates

[Imp0ssibleGirl9]

Using Windows 11 calibre 64bit version 9.15.0
iPad Air M3 IOS 20.6.2 with Calibre Companion app Version 3.0
Last time everything synced correctly was 9/16/26

Issue: This all happened suddenly as everything was working a week ago. I am now unable to sync my books between my PC and iPad when doing it as a wireless device.

I have calibre open on my PC and have CC on my ipad. I click connect as a wireless device on CC iPad and Calibre on PC. BOTH show that it is connected and starts syncing.
Then suddenly it stops and throws errors.

iPad CC shows: "Error Unknown error. Please make sure you have the latest version of Calibre and CC."

Calibre on PC throws 2 different errors.
1. "error No Space on device Cannot upload books to device there is no more free space available in main memory." (it lists 3 books already on ipad and there is more than 55GB free space on my iPad)

2. Error Communicating with device calibre, version 9.15.0
ERROR: Error: Error communicating with device

Device closed the network connection

Traceback (most recent call last):
File "calibre\devices\smart_device_app\driver.py", line 690, in _call_client
File "calibre\devices\smart_device_app\driver.py", line 656, in _send_byte_string
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "calibre\gui2\device.py", line 107, in run
File "calibre\gui2\device.py", line 632, in _sync_booklists
File "calibre\devices\smart_device_app\driver.py", line 60, in _synchronizer
File "calibre\devices\smart_device_app\driver.py", line 1343, in free_space
File "calibre\devices\smart_device_app\driver.py", line 60, in _synchronizer
File "calibre\devices\smart_device_app\driver.py", line 701, in _call_client
calibre.devices.errors.ControlError: Device closed the network connection



Actions Taken so far
1. Quit calibre and restarted on both PC and iPad
2. Made sure both CC and Calibre are updated. They are and were done so recently. I actually think it was the updates that broke it. CC was updated to 3.0 today 9/21/26. I tried syncing and got the errors so I updated Calibre on pc to 9.15 and got the exact same errors.
3. Rebooted PC and relaunched Calibre on pc. Same errors
4. Deleted the 3 books from Calibre on my PC. They are still on my iPad and have been there for 4+years. After deleting books from Calibre on PC, I tried to sync again. It no longer throws the "no space on device error" but still throws the error about communicating with device.
calibre, version 9.15.0
ERROR: Error: Error communicating with device

Device closed the network connection

Traceback (most recent call last):
File "calibre\devices\smart_device_app\driver.py", line 690, in _call_client
File "calibre\devices\smart_device_app\driver.py", line 656, in _send_byte_string
ConnectionResetError: [WinError 10054] An existing connection was forcibly closed by the remote host

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "calibre\gui2\device.py", line 107, in run
File "calibre\gui2\device.py", line 631, in _sync_booklists
File "calibre\devices\smart_device_app\driver.py", line 60, in _synchronizer
File "calibre\devices\smart_device_app\driver.py", line 1497, in sync_booklists
File "calibre\devices\smart_device_app\driver.py", line 60, in _synchronizer
File "calibre\devices\smart_device_app\driver.py", line 701, in _call_client
calibre.devices.errors.ControlError: Device closed the network connection


Honestly think its Calibre Companion that updated and broke things but have no clue how I could downgrade the app on my iPad or if it was possible. I did send the CC debug logs inside the app. I can still do the content server and access my books that way but its not the same and honestly prefer having my books already downloaded on my device so I can read the next book(s) in the series even if i am away from wifi connection.

Any help would be appreciated.

[PeterT]

I suggest posting in the archived Calibre Companion forum. Sam has reappeared and posted that there are updated versions for both IOS and Android