e-viewer stopped opening epubs

emfril · 04-12-2026, 09:58 PM

After the last 2 updates the calibre e-viewer does not open epubs. Is it only me or others have the same problem? What should I do about it?

kovidgoyal · 04-12-2026, 10:12 PM

Provide more details, what does stopped opening epubs mean. What happens when you try to opena n epub. On what OS?

BetterRed · 04-12-2026, 10:13 PM

If Windows or MacOS - which version. If Linux which one and which desktop manager.

BR

emfril · 04-13-2026, 03:35 AM

Laptop Windows 11. Calibre version: I downloaded 2 new versions the last few days (there is no About to click and find the version number). When I click an epub file nothing happens. The In the Task Manager
calibre worker process
and
The calibre e-book viewer
appear but nothing appears on the desktop.

JSWolf · 04-13-2026, 07:07 AM

Quote:

Originally Posted by emfril

Laptop Windows 11. Calibre version: I downloaded 2 new versions the last few days (there is no About to click and find the version number). When I click an epub file nothing happens. The In the Task Manager
calibre worker process
and
The calibre e-book viewer
appear but nothing appears on the desktop.

The version is in the lower left of the main GUI.

DNSB · 04-13-2026, 03:26 PM

Are you sure that your calibre ebook-viewer is appearing on screen? If you see ebook viewer icon in the task bar, try one of the methods for moving an off screen window back to the screen. Hold shift and right-click on the taskbar icon and then move, hover on the taskbar icon, right click on the preview and then move, etc.

emfril · 04-13-2026, 11:56 PM

calibre: version 9.7. Windows version 25H2
I wrote that the e-book reader appears in the *Task Manager*, among the processes. It does *not* appear in the Task Bar.

BetterRed · Yesterday, 12:24 AM

Try restarting in Windows Safe Mode.

Viewer is working fine here — Win 10 Pro 25H2, calibre 9.7.

BR

kovidgoyal · Yesterday, 12:25 AM

Run it as

calibre-debug -w

from a command prompt that will show you debug output about what it is doing.

emfril · Yesterday, 09:52 AM

I got an alert!

================
calibre, version 9.7.0
ERROR: Loading book failed: Failed to open the book at C:\My Stuff\My Files\My E-Book Library\epub\The_Making_of_an_Elder_Culture.epub. Click "Show details" for more info.

Traceback (most recent call last):
File "calibre\gui2\viewer\ui.py", line 577, in _load_ebook_worker
File "calibre\gui2\viewer\convert_book.py", line 255, in prepare_book
File "calibre\gui2\viewer\convert_book.py", line 210, in do_convert
File "subprocess.py", line 1220, in communicate
File "subprocess.py", line 1653, in _communicate
File "threading.py", line 1124, in join
RuntimeError: cannot join thread before it is started

kovidgoyal · Yesterday, 10:37 AM

Definitely try rebooting in safe mode.

04-12-2026, 09:58 PM	#1
emfril Junior Member Posts: 8 Karma: 10 Join Date: Jun 2016 Device: kindle reader	e-viewer stopped opening epubs After the last 2 updates the calibre e-viewer does not open epubs. Is it only me or others have the same problem? What should I do about it?

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04-12-2026, 10:12 PM	#2
kovidgoyal creator of calibre Posts: 46,194 Karma: 29626604 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Provide more details, what does stopped opening epubs mean. What happens when you try to opena n epub. On what OS?

04-12-2026, 10:13 PM	#3
BetterRed null operator (he/him) Posts: 22,582 Karma: 32600660 Join Date: Mar 2012 Location: Sydney Australia Device: none	If Windows or MacOS - which version. If Linux which one and which desktop manager. BR

04-13-2026, 03:35 AM	#4
emfril Junior Member Posts: 8 Karma: 10 Join Date: Jun 2016 Device: kindle reader	Laptop Windows 11. Calibre version: I downloaded 2 new versions the last few days (there is no About to click and find the version number). When I click an epub file nothing happens. The In the Task Manager calibre worker process and The calibre e-book viewer appear but nothing appears on the desktop.

04-13-2026, 03:26 PM	#6
DNSB Bibliophagist Posts: 51,252 Karma: 179232776 Join Date: Jul 2010 Location: Vancouver Device: Kobo Sage, Libra Colour, Lenovo M8 FHD, Paperwhite 4, Tolino epos	Are you sure that your calibre ebook-viewer is appearing on screen? If you see ebook viewer icon in the task bar, try one of the methods for moving an off screen window back to the screen. Hold shift and right-click on the taskbar icon and then move, hover on the taskbar icon, right click on the preview and then move, etc.

04-13-2026, 11:56 PM	#7
emfril Junior Member Posts: 8 Karma: 10 Join Date: Jun 2016 Device: kindle reader	calibre: version 9.7. Windows version 25H2 I wrote that the e-book reader appears in the Task Manager, among the processes. It does not appear in the Task Bar.

Yesterday, 12:24 AM	#8
BetterRed null operator (he/him) Posts: 22,582 Karma: 32600660 Join Date: Mar 2012 Location: Sydney Australia Device: none	Try restarting in Windows Safe Mode. Viewer is working fine here — Win 10 Pro 25H2, calibre 9.7. BR

Yesterday, 12:25 AM	#9
kovidgoyal creator of calibre Posts: 46,194 Karma: 29626604 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Run it as calibre-debug -w from a command prompt that will show you debug output about what it is doing.

Yesterday, 09:52 AM	#10
emfril Junior Member Posts: 8 Karma: 10 Join Date: Jun 2016 Device: kindle reader	I got an alert! ================ calibre, version 9.7.0 ERROR: Loading book failed: Failed to open the book at C:\My Stuff\My Files\My E-Book Library\epub\The_Making_of_an_Elder_Culture.epub. Click "Show details" for more info. Traceback (most recent call last): File "calibre\gui2\viewer\ui.py", line 577, in _load_ebook_worker File "calibre\gui2\viewer\convert_book.py", line 255, in prepare_book File "calibre\gui2\viewer\convert_book.py", line 210, in do_convert File "subprocess.py", line 1220, in communicate File "subprocess.py", line 1653, in _communicate File "threading.py", line 1124, in join RuntimeError: cannot join thread before it is started

Yesterday, 10:37 AM	#11
kovidgoyal creator of calibre Posts: 46,194 Karma: 29626604 Join Date: Oct 2006 Location: Mumbai, India Device: Various	Definitely try rebooting in safe mode.