Thanks Matthew

You were right

Opening the epub in Sigil showed some errors that Sigil corrected

I just needed to save the epub, launch a scan and it worked !!

Many thanks

Here's my System Info :

Ubooquity version: 2.1.2 built on 2018-10-14 at 12:58
Java version: 1.8.0_181
Java vendor: Oracle Corporation
Java VM name: Java HotSpot(TM) Client VM
OS name: Windows 10
OS version: 10.0
OS architecture: x86
Number of processors: 24
Max memory: 247 MB
Free memory: 46 MB
Total memory: 128 MB
isUserManagementEnabled: false
comicWidth: 160
comicHeight: 230
comicsPaginationNumber: 30
bookWidth: 160
bookHeight: 230
booksPaginationNumber: 30
autoscanPeriod: 0
isRemoteAdminEnabled: false
theme: Default
reverseProxyPrefix: false
keystorePath: false
keystorePassword: true
isOpdsProviderEnabled: false
scanExclusionPattern: false
bypassSingleRootFolder: true
window.innerWidth: 982
window.innerHeight: 795
window.outerWidth: 1006
window.outerHeight: 920
window.devicePixelRatio: 1
navigator.userAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36 Edg/119.0.0.0
navigator.platform: Win32
navigator.language: en-US
screen.availWidth: 1920
screen.availHeight: 1040
screen.width: 1920
screen. Height: 1080